Radio communication system, radio communication device, radio communication method, and computer program

ABSTRACT

A scrambling initial value is shared without deteriorating transmission efficiency. On the transmission side, a scrambling initial value is created based on a part of a physical layer header not scrambled, a transmission signal sequence scrambled is created by calculating an exclusive-OR operation between a scrambled sequence generated from the scrambling initial value and a transmission data sequence, and is transmitted. On the reception side, the same descrambling initial value as the scrambling initial value is created based on a part of a physical header of a reception frame, and a reception data sequence is descrambled by calculating an exclusive-OR operation between a descrambled sequence generated from this descrambling initial value and a reception signal sequence scrambled.

TECHNICAL FIELD

The present invention relates to a wireless communication system,wireless communication apparatus and wireless communication method, andcomputer program for performing mutual communication between multiplewireless stations, such as a wireless LAN (Local Area Network), andparticularly relates to a wireless communication system, wirelesscommunication apparatus and wireless communication method, and computerprogram for mutually performing scrambling/descrambling between a datatransmission station and a data reception station.

In further detail, the present invention relates to a wirelesscommunication system, wireless communication apparatus and wirelesscommunication method, and computer program for appropriately performingscrambling/descrambling using a correct scrambling initial value betweentransmission and reception, and particularly relates to a wirelesscommunication system, wireless communication apparatus and wirelesscommunication method, and computer program for sharing a scramblinginitial value between transmission and reception without deterioratingthe original transmission efficiency of user data which a user wants totransmit.

BACKGROUND ART

Wireless LANs have attracted a great deal of attention as a system forliberating users from LAN cables of the wired method. According to awireless LAN, the most part of cables in the work space such as anoffice can be omitted, so communication terminals such as personalcomputers (PC) can be moved with relative ease. In recent years, thedemand thereof has markedly increased, accompanying the increase speedsand reduced prices of wireless LAN systems. Particularly, in these days,implementation of personal area networks (PAN) has been studied forestablishing a small-scale wireless network between multiple electronicapparatuses present around a personal environment to perform informationcommunication. For example, different wireless communication systems andwireless communication apparatuses have been stipulated by usingfrequency bands not requiring the authorization of a competentauthority, such as the 2.4-GHz band, 5-GHz band, or the like.

Examples of the standard specifications relating to a wireless networkinclude IEEE (The Institute of Electrical and Electronics Engineers)802.11 (e.g., see Non-patent Document 1), HiperLAN/2 (e.g., seeNon-patent Document 2 and Non-patent Document 3), IEEE802.15.3, andBluetooth communication. As for the IEEE802.11 standard, expansionstandards such as IEEE802.11a (e.g., see Non-patent Document 4),IEEE802.11b, and IEEE802.11g are available according to the differencesof wireless communication methods and frequency bands to be used.

With a wireless communication system, multi-bus environment is formedwherein a combination of multiple reflected waves and delayed waves isreceived at a data reception station in addition to the direct wave froma data transmission station side. Delay distortion (or frequencyselective phasing) is caused due to the multi-bus, and error is causedover communication. This results in a problem wherein inter-symbolinterference due to delay distortion is caused.

Major countermeasures of delay distortion include a multi-carriertransmission method represented with the OFDM modulation. With the OFDM(Orthogonal Frequency Division Multiplexing) method, the frequency ofeach carrier is set such that the respective carriers are mutuallyorthogonal within a symbol zone. When transmitting information,information transmitted in serial is subjected to serial-to-parallelconversion for each symbol cycle slower than the informationtransmission rate, the multiple converted output data is assigned toeach carrier to perform amplitude and phase modulation for each carrier,the data is converted into time axial signals while keeping theorthogonality of each carrier by performing inverse FFT regarding themultiple carriers, and transmitted. Also, when receiving information,the operations opposite of this, i.e., time axial signals are convertedinto frequency axial signals by performing FFT to perform demodulationcorresponding to each modulation method regarding each carrier, and thenare subjected to parallel-to-serial conversion to reproduce the originalinformation transmitted with serial signals. The OFDM modulation methodhas been employed as the standard specifications of a wireless LAN inIEEE802.11a/g, for example.

Also, as another problem in a wireless communication system, there is aproblem wherein a linear frequency spectrum is formed by data of 0through 1 extremely continuing. For example, in the event of employingthe OFDM modulation method, a configuration is made up of multiple subcarriers, the difference between average power and peak power is great,resulting in shortage of an power range on the transmission side and onthe reception side. To this end, scrambling is usually performed forpseudo-randomizing data over a transmission path.

In general, on the transmission side, scrambling is performed bycalculating an exclusive-OR operation between delivery data andpseudo-random bits, the output thereof is taken as transmission data. Onthe other hand, on the reception side, descrambling is performed bycalculating an exclusive-OR operation between received data andpseudo-random bits, whereby the transmission data can be extracted. Atthis time, the transmission side and the reception side must have thesame pseudo-random bit generator, and also have the same initial valuethereof.

Examples of a wireless communication system for performing scramblinginclude IEEE802.11a, which is the technical standard of a wireless LAN.In FIG. 32, a configuration example of a wireless communicationapparatus, which is employed for IEEE802.11a. This wirelesscommunication apparatus performs, for example, audio communication as toanother wireless communication apparatus (not shown) corresponding toIEEE802.11a. Hereinafter, description will be made regarding thewireless communication operations thereof with reference to FIG. 32.

First, description will be made regarding operation of the transmissionsystem following the flow of signals. In the event of data communicationsuch as being connected to a computer, a data signal such as audio isinput to a data input/output processing unit 102, and the signal isconverted into an appropriate digital data sequence.

Subsequently, the data sequence is input to a transmission dataprocessing unit 110. If necessary, the transmission data processing unit110 receives communication control data to be transmitted to a wirelesscommunication apparatus (not shown) serving as an other party ofwireless communication from a control unit 104, subjects this tomultiplexing as appropriate, and then forms and outputs frame and slotconfigurations for transmitting this in a wireless zone.

Subsequently, a CRC (Cyclic Redundancy Check) adder 112 adds redundancyfor detecting an error on the reception side to the transmission data,and further, a cipher device 114 subjects the transmission data toencryption, and outputs this.

Subsequently, a scrambler 116 subjects the transmission data toscrambling so as to form pseudo-random in accordance with apredetermined algorithm (described later). Also, a header generator 117generates a PHY (physical layer) header. Subsequently, an encoder 118subjects the PHY header and the transmission data subjected toscrambling to convolution encoding, and further an interleaver 120subjects this to interleaving. According to this interleavingprocessing, the coded bit sequence is rearranged in accordance with aparticular rule, so on the reception side, burst errors can be convertedinto random errors by performing an inverse operation, i.e.,de-interleaving (described later).

Subsequently, a modulator 122 subjects the transmission data to mappingto signal points at the time of transmission, and outputs inphasecomponents (I components) and orthogonal components (Q components). Acomplex IFFT unit 124 subjects the output thereof to inverse FFT,thereby performing the OFDM modulation.

Subsequently, a time-waveform trimming unit 126 provides guard time byadding a cycle prefix, and subjects the output data to window wingprocessing so as to smooth the rise and decay of the OFDM modulationsymbol.

Subsequently, a DA converter 128 converts the transmission data from adigital waveform to an analog waveform, and further, an RF transmitter130 subjects the transmission data to filtering, vector modulation usingthe I components and Q components, a frequency conversion to anappropriate transmission frequency channel, control of transmissionpower, amplification, and so forth.

The transmission signal up-converted by the RF transmitter 130 is inputto an antenna 134 via an antenna duplexer 132, and finally transmittedfrom the antenna 134 as an electromagnetic wave. This transmissionsignal is received by a other party of wireless communication (notshown).

Note that the antenna duplexer 134 is used for separating a transmissionsignal and a reception signal, an antenna switch is employed in the TDDmethod and the FDD/TDMA method, and a duplexer is generally employed inthe other methods. Now, let us say that an antenna switch is employed,since the example here is IEEE802.11a of the TDD method.

Next, description will be made regarding the operation of the receptionsystem in detail. Now, let us say that a wireless communicationapparatus 100 receives a transmission signal generated by anotherwireless communication apparatus serving as an other party of wirelesscommunication (not shown) performing the same processing as thetransmission system in the above IEEE802. 11a.

The transmission signal from the other party of wireless communicationis received at the antenna 134 as an electromagnetic wave. The signal isseparated from the own transmission signal at the antenna duplexer 132,following which is input to an RF receiver 140. The RF receiver 140subjects the reception signal to amplification, attenuation ofunnecessary frequency components, selection of a desired frequencychannel, frequency conversion, reception signal amplitude level control,vector detection process for separating the I components and the Qcomponents, band limit, and the like, and thus the I components and theQ components of the reception signal are extracted.

An AD converter 142 converts the reception signal down-converted by theRF receiver 140 from an analog waveform to a digital waveform.Subsequently, a synchronization circuit 144 subjects the reception datato frame synchronization, frequency error correction, and the like. Now,in the event of searching a communicable communication other partyimmediately after power is turned on or the like, detection of asynchronous signal or initial synchronization is performed using thissynchronization circuit 144. Various arrangements have been proposedregarding initial synchronization, frame synchronization, frequencyerror correction, and the like, but these are not directly associatedwith the essence of the present invention, so further description willnot be made in the present specification.

Subsequently, a time-waveform trimming unit 146 subjects the receptiondata to time waveform trimming so as to remove guard time provided byadding a cycle prefix, following which a complex FFT unit 148 subjectsthe reception data to FFT to perform the OFDM demodulation.

Subsequently, an equalizer 150 performs equalization using estimation ofa transmission path and estimation results. In some cases, the equalizer150 inputs the information of the synchronization circuit 144, and usesthis for estimation of a transmission path, or the like. Note thatvarious arrangements have been proposed as an equalizer, but these arenot directly associated with the essence of the present invention, sofurther description will not be made in the present specification.

The output of the equalizer 150 is input to a demodulator 152, and issubjected to signal point determination to output a reception bitestimation value. Subsequently, the reception data is input to ade-interleaver 154, and is subjected to de-interleaving for rearrangingthe coded bit sequence in accordance with a particular rule.Subsequently, a decoder 156 performs decoding of error correction codessubjected on the transmission side.

Subsequently, a descrambler 158 subjects the decoded reception data todescrambling, which is inverse conversion of scrambling performed on thetransmission side. Also, a header extractor 157 extracts a PHY headerfrom the decoded reception data. Further, a decipher device 160deciphers encryption subjected on the transmission side, following whicha CRC checking unit 162 outputs the reception data of which a CRC isremoved, and the result of a CRC check regarding the reception block.

Subsequently, in the event that determination is made that the result ofthe CRC check of the reception block has no error, a reception dataprocessing unit 164 removes the frame configuration and slotconfiguration subjected for transmission in a wireless zone.Subsequently, in the event of data communication such as connected witha computer, the data input/output processing unit 102 converts thereception data into a data signal, and outputs this.

In the event that the reception data includes communication control datatransmitted from an other party of wireless communication (not shown),that portion is extracted by the reception data processing unit 164, andis input to the control unit 104 via a reception system control line106. Subsequently, the control unit 104 interprets the received controldata, and performs operation control of each unit within the wirelesscommunication apparatus 100 in accordance with the received instruction.

Each unit of the transmission system is connected to the control unit104 via a transmission system control line 108. Accordingly, the controlunit 104 can perform various operation control and monitoring of thetransmission system such as on/off control of the transmission system,operation control and status monitoring of the RF transmitter 130, fineadjustment of transmission timing, modification of an encoding method orsignal point mapping method, control of retransmission, and the like viathe transmission system control line 108.

Also, each unit of the reception system is connected to the control unit104 via the reception system control line 106. Accordingly, the controlunit 104 can perform operation control and monitoring of variousreception systems such as on/off control of the reception system,operation control and status monitoring of the RF receiver 140, fineadjustment of reception timing, modification of a decoding method orsignal point demapping method, control of retransmission, and the likevia the reception system control line 106.

FIG. 33 illustrates the configuration of the scrambler 116 disposed inthe transmission system of the wireless communication apparatus 100. Thescrambler 116 shown in the drawing is made up of a 7-stage shiftregister, and an arrangement is made wherein X¹ is the lowest bit, X⁷ isthe highest bit, and the value of each bit is shifted to the adjacenthigher bit X² through X⁷ in order. As for the highest bit X⁷, anexclusive-OR operation between the output from the X⁴ and the outputfrom the X⁷ is calculated, and the result is input to the lowest bit X¹.At the same time, an exclusive-OR operation between the result and inputdata is calculated, and this result is output as data followingscrambling.

Data other than 0000000 (i.e., all zeroes) is employed for the X¹through X⁷ shown in FIG. 33. This is because all-zero data cannot serveas a scrambler. In other words, the total number of a bit sequence,which can be employed, is 2⁷−1=127, and any number of these may beemployed. A scrambling pattern, which occurs through scrambling, can bechanged by modifying the initial value of scrambling.

Also, FIG. 34 illustrates the configuration of the descrambler 158disposed in the reception system of the wireless communication apparatus100. The descrambler shown in the drawing has completely the sameconfiguration as the scrambler shown in FIG. 24, stores the initialvalue provided from the transmission side to the X¹ through X⁷, andcalculates an exclusive-OR operation between the stored initial valueand received input data, thereby performing descrambling.

FIG. 35 illustrates the format of the OFDM signal stipulated byIEEE802.11a. As shown in the drawing, the Preamble is transmitted first,and subsequently, the SIGNAL field is transmitted with one OFDM symbol,and further subsequently, the DATA field is transmitted.

The PHY header of IEEE802. 11a comprises the above-described SIGNALfield, and the Service field made up of 16 bits on the MSB side of theDATA field. FIG. 36 illustrates the configuration of the PHY header indetail. As shown in the drawing, the SIGNAL field comprises themodulation method, RATE information of 4 bits determined from theencoding rate of error correction codes, a reserved bit of one bit,LENGTH information of 14 bits indicating the length of a transmissionpacket, PARITY information of one bit for detecting a bit error of theSIGNAL field, and TAIL bits of 6 bits for terminating a convolutioncode. Here, the PARITY bit is set such that the number of “ones”included in the bit sequence made up of the RATE information, thereserved bit, the LENGTH information, and the PARITY bit becomes even.

Following the SIGNAL field, the Service field of 16 bits continues, andof these 16 bits, 7 bits from the MSB side are used for transmission ofthe initial value of scrambling, i.e., notification, and this isequivalent to the initial value provided for descrambling on thereception side. Incidentally, the residual 9 bits of the Service fieldare reserved.

The SIGNAL field is transmitted by BPSK R1/2 of which the required Eb/Nois the lowest, of the modulation modes stipulated by IEEE802.11a. The 24bits of the SIGNAL field are equivalent to 48 (sub carriers)×½ (encodingrate)=24 bits in the event of transmitting data carrier and 48 subcarriers by BPSK R1/2 using the OFDM transmission, and are transmittedwith one OFDM symbol. This SIGNAL field is not subjected to scrambling.

The subsequent data field hereafter is transmitted in a state of beingsubjected to scrambling with the modulation mode indicated by the RATEfield within the SIGNAL field.

Now, description will be made further in detail regarding handling ofthe scrambling initial value on the transmission side, and thedescrambling initial value on the reception side. Scrambling anddescrambling are realized by combining a shift register and anexclusive-OR circuit according to a generator polynomial representingpseudo-random number sequence (e.g., see Patent Document 1).

FIG. 37 illustrates the configuration of around the scrambler 116 on thetransmission side in detail. Transmission data is scrambled bycalculating an exclusive-OR between the transmission data and ascrambling pattern generated with a later-described method at an EXOR116 b within the scrambler 116 following the transmission data beingencrypted at the cipher device 114. The output thereof is subjected toerror correction encoding at the encoder 118.

When starting scrambling, a scrambling pattern generator 116 a receivesnotification from the control unit 104 regarding a scrambling initialvalue at the time of generating a scrambling pattern. The scramblinginitial value notified is set within the register of the scrambler bodymade up of a shift register such as shown in FIG. 33, and a scramblingpattern is generated while the value within the register is shifted foreach clock.

In particular, as for the first 7 bits of the Service field disposed inthe headmost of the DATA field for transmitting a scrambling pattern,“0” data of 7 bits is entered at the time of outputting from the cipherdevice 114, and the first 7 bits of the Service field are generated bycalculating an exclusive-OR operation between this data and a scramblingpattern to be generated from the scrambling initial value, which is set,for each bit.

However, the input data was all “0”, so the first 7 bits of the outputof the EXOR 116 b are the same as the scrambling initial value, which isset. On the reception side, which received this data, the 7 bits of thisfield can be used as a descrambling initial value.

FIG. 38 illustrates the configuration of around the descrambler 158 onthe reception side in detail. Reception data is descrambled bycalculating an exclusive-OR between the reception data and adescrambling pattern generated with a later-described method at an EXOR158 b within the descrambler 158 following the reception data beingsubjected to error correction decoding at the decoder 156. The outputthereof is deciphered at the decipher device 160.

When starting descrambling, the 7 bits from the MSB side of the Servicefield disposed in the headmost of the received DATA field are extractedas the initial value thereof, and are set within the register of thedescrambler body made up of a shift register such as shown in FIG. 34,and a descrambling pattern is generated while the value within theregister is shifted for each clock.

Thus, with IEEE802. 11a, the initial value 7 bits of scrambling areconfigured so as to be transmitted using the Service field within thePHY header section, which is not scrambled, and thus, the samescrambling initial value and the same descrambling initial value can beshared between transmission and reception, thereby performing scramblingand descrambling correctly. However, a method for transmitting thescrambling initial value thus using the data section is equivalent to amethod for storing data different from the user data, which a useractually wants to send, in the data section and transmitting this, sotransmission efficiency is deteriorated by the difference thereof, whichis not preferable.

Also, with the transmission format of IEEE802. 11a, one OFDM symbol fortransmitting the SIGNAL field employs the BPSK modulation of whichrequired S/N is low, and encoding rate=½, but the DATA field including ascrambling initial value tends to be transmitted with a modulationmethod of which required S/N is higher than the above S/N, and encodingrate higher than the above rate, so bit error is readily caused.

Also, as for the SIGNAL field and the entire data, error correction isperformed at a physical layer using convolution codes. As for a decodingmethod of convolution codes, the Viterbi decoding method has been known.

On the other hand, even if such error countermeasures are performed, itis difficult to completely correct an error, and accordingly, it isnecessary to request the transmission device side of retransmission inthe event of detecting an uncorrectable error on the reception deviceside. Increase of such repetitions of retransmission may affectcommunication speed. For example, when performing streaming transmissionof moving image data or the like such as QoS (Quality of Service), itbecomes difficult to reserve a communication band and assure a constantspeed. Accordingly, in order to deal with the QoS function, as for MAC(Medium Access Control) sublayer data, i.e., the PSDU of data, it can beconceived to implement error correction processing as a MAC sublayer.Block codes such as Reed-Solomon product codes can be employed for sucherror correction.

However, even if error correction corresponding to the QoS isimplemented to the MAC sublayer, synchronization between scrambling anddescrambling is not normally performed in the event that countermeasuresare not performed regarding the Service, the PSDU may not be descramblednormally on the reception device side. In the event that descrambling isnot normally performed, consequently the transmission side is requestedof retransmission of data, and even if an error correction correspondingto the QoS is implemented, the effect thereof cannot be obtained. Asdescribed above, it can be conceived that transmission in a modulationmode having high error tolerance is not assured regarding the Service,so the Service has high possibility to cause an error as compared to theSIGNAL.

As one method for preventing deterioration of transmission efficiencydue to notification of a scrambling initial value, a technique forreferring to an MAC address, and employing a part thereof as ascrambling initial value has been proposed (e.g., see Patent Document2). In this case, it is not necessary to bother to transmit a scramblinginitial value using the data section.

However, with this method, the MAC address itself cannot be scrambled,which causes a problem from the perspective of concealment. Also, thatthe MAC address itself cannot be scrambled means that if “0” and “1”within the data form a biased distribution during transmission of theMAC address, it cannot be converted into a random bit sequence, andconsequently, the possibility that linear components occur in thespectrum of that zone remains.

Further, with IEEE802.11a, the MAC header including the PHY header, theMAC address, and the like is clearly separated, and in the event ofapplying the above scrambling notification method to such a wirelesscommunication system, in addition to the MAC address being described inthe DATA section, further a part of the MAC address is used for the PHYheader section, which causes redundancy.

[Patent Document 1]

Japanese Unexamined Patent Application Publication No. 2000-269944

[Patent Document 2]

Japanese Unexamined Patent Application Publication No. 8-107414

[Non-patent Document 1]

International Standard ISO/IEC 8802-11: 1999(E) ANSI/IEEE Std 802.11,1999 Edition, Part11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications

[Non-patent Document 2]

ETSI Standard ETSI TS 101 761-1 V1.3.1 Broadband Radio Access Networks(BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part1: BasicData Transport Functions

[Non-patent Document 3]

ETSI TS 101 761-2 V1.3.1 Broadband Radio Access

Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part2:Radio Link Control (RLC) sublayer

[Non-patent Document 4]

Supplement to IEEE Standard for Informationtechnology-Telecommunications and information exchange betweensystems-Local and metropolitan area networks-Specificrequirements-Part11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) specifications: High-speed Physical Layer in the 5GHZ Band

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

The present invention provides an excellent wireless communicationsystem, wireless communication apparatus and wireless communicationmethod, and computer program, which allow a data transmission stationand a data reception station to preferably performscrambling/descrambling respectively.

The present invention further provides an excellent wirelesscommunication system, wireless communication apparatus and wirelesscommunication method, and computer program, which allow betweentransmission and reception to preferably perform scrambling/descramblingusing a correct scrambling initial value.

The present invention further provides an excellent wirelesscommunication system, wireless communication apparatus and wirelesscommunication method, and computer program, which allow betweentransmission and reception to share a scrambling initial value withoutdeteriorating transmission efficiency of user data which a user actuallywants to transmit.

The present invention further realizes synchronization between ascrambler and a descrambler with high error tolerance in a generalpurpose communication system such as conforming to the IEEE802.11a, forexample.

Means for Solving the Problems

The present invention has been made in light of the above problems, andaccording to a first aspect thereof, a wireless communication system forcommunicating transmission data comprises: a physical layer headersection; and a data section;

wherein on the transmission side, a scrambling initial value isgenerated using at least a part of a physical header section, andscrambling of a data section is performed using the scrambling initialvalue;

and wherein on the reception side, a descrambling initial value isgenerated using at least a part of a physical header section, anddescrambling of a data section is performed using the descramblinginitial value.

Note however, that the term “system” here means a logical group made upof multiple devices (or function modules for realizing a particularfunction), and whether or not each device or each function module isaccommodated in a single casing is not of concern.

With a wireless communication system according to the present invention,on the transmission side, a scrambling initial value is created based ona part of a physical layer header not scrambled, a transmission signalsequence scrambled is created by calculating an exclusive-OR operationbetween a scrambled sequence generated from the scrambling initial valueand a transmission data sequence, and transmitted. On the other hand, onthe reception side, the same descrambling initial value as thescrambling initial value is created based on a part of a physical headerof a reception frame, an exclusive-OR operation between a descrambledsequence generated from this descrambling initial value and a receptionsignal sequence scrambled is calculated, whereby a reception datasequence can be descrambled.

According to the present invention, a scrambling initial value can beshared between transmission and reception using the information of aphysical header section not scrambled within a transmission frame.Accordingly, a dedicated field does not need to be included in atransmission data frame for notifying the scrambling initial value, andthe scrambling initial value can be shared between transmission andreception without deteriorating the transmission efficiency of user datawhich a user actually wants to send.

With a wireless communication system according to the present invention,a wireless communication apparatus serving as a communication stationgenerates an initial value when scrambling or descrambling using atleast a part of a physical layer header section based on a rule commonwith an other party of communication, and can perform scrambling ordescrambling of the data section using this initial value.

At the time of transmission, a transmission signal sequence scrambled isgenerated by calculating an exclusive-OR operation between a scrambledsequence generated from a scrambling initial value and a transmissiondata sequence. Also, at the time of reception, a reception data sequenceis descrambled by calculating an exclusive-OR operation between adescrambled sequence generated from a descrambling initial value and areception signal sequence scrambled.

For example, in the event that an initial value whenscrambling/descrambling is n bits in length (wherein n is a naturalnumber), an n-bit sequence obtained by extracting n bits from a physicallayer header section or a part thereof based on a rule common with another party of communication can be taken as the initial value whenscrambling/descrambling. At this time, the initial value whenscrambling/descrambling is preferably generated by extracting n bitsincluding fields which are not all zero bits within the physical layerheader section, in light of the field configuration of the physicallayer header section.

Here, in the event that n bits extracted from the physical layer headersection are all zero bits, a fixed n-bit sequence, which are not allzero bits, shared with an other party of communication may be taken asthe initial value when scrambling/descrambling.

Also, in the event that the initial value when scrambling/descramblingis n bits in length (wherein n is a natural number), (n−k) bits from aphysical layer header section or a part thereof based on a rule commonwith an other party of communication are extracted (wherein k is anatural number smaller than n), and a k-bit sequence such that at least1 bit thereof includes the logic “1”, shared with the other party ofcommunication is inserted in the extracted bit sequence of the (n−k)bits in a pattern shared with the other party of communication, wherebythe initial value when scrambling/descrambling can be generated.

Alternatively, in the event that the initial value whenscrambling/descrambling is n bits in length (wherein n is a naturalnumber), the number of logics “1” in the physical layer header sectionor a part thereof is counted, the number thereof is represented with nbits in binary, whereby this can be taken as the initial value whenscrambling/descrambling. However, in the event that the number of logics“1” counted in the physical layer header section or a part thereof iszero, a fixed n-bit sequence, which are not all zero bits, shared withan other party of communication may be taken as the initial value whenscrambling/descrambling.

Also, in the event that the initial value when scrambling/descramblingis n bits in length (wherein n is a natural number), an arrangement maybe made wherein the number of logics “1” in the physical layer headersection or a part thereof is counted, the number thereof is representedwith (n−m) bits in binary (wherein m is a natural number smaller thann), an m-bit sequence such that at least 1 bit thereof includes logic“1”, shared with an other party of communication is inserted in theextracted bit sequence of the (n−m) bits in a pattern shared with theother party of communication, thereby generating the initial value whenscrambling/descrambling.

Also, in the event that the initial value when scrambling/descramblingis n bits in length (wherein n is a natural number), an arrangement maybe made wherein the number of logics “1” in the physical layer headersection or a part thereof is counted, x shared with an other party ofcommunication (wherein x is a natural number smaller than 2^(n)) isadded to the number thereof, the result is represented with n bits inbinary, and this bit sequence is taken as the initial value whenscrambling/descrambling.

Also, in the event that the initial value when scrambling/descramblingis n bits in length (wherein n is a natural number), an arrangement maybe made wherein the number of logics “0” in the physical layer headersection or a part thereof is counted, the number thereof is representedwith n bits in binary, and this is taken as the initial value whenscrambling/descrambling. However, in the event that the number of logics“0” counted in the physical layer header section or a part thereof iszero, a fixed n-bit sequence, which are not all zero bits, shared withan other party of communication may be taken as the initial value whenscrambling/descrambling.

Also, in the event that the initial value when scrambling/descramblingis n bits in length (wherein n is a natural number), an arrangement maybe made wherein the number of logics “0” in the physical layer headersection or a part thereof is counted, the number thereof is representedwith (n−m) bits in binary (wherein h is a natural number smaller thann), an h-bit sequence such that at least one bit thereof is logic “1”,shared with an other party of communication is inserted in the extractedbit sequence of the (n−h) bits in a pattern shared with the other partyof communication, thereby generating the initial value whenscrambling/descrambling.

Also, in the event that the initial value when scrambling/descramblingis n bits in length (wherein n is a natural number), an arrangement maybe made wherein the number of logics “0” in the physical layer headersection or a part thereof is counted, y shared with an other party ofcommunication (wherein y is a natural number smaller than 2^(n)) isadded to the number thereof, the result is represented with n bits inbinary, and this bit sequence is taken as the initial value whenscrambling/descrambling.

Also, in the event that the initial value when scrambling/descramblingis n bits in length (wherein n is a natural number), an arrangement maybe made wherein the number of logics “1” and the number of logics “0” inthe physical layer header section or a part thereof are countedrespectively, and the absolute value of the difference thereof isrepresented with n bits in binary, and this is taken as the initialvalue when scrambling/descrambling. However, in the event that thedifference between the number of logics “1” and the number of logics “0”in the physical layer header section or a part thereof is zero, a fixedn-bit sequence, which are not all zero bits, shared with an other partyof communication may be taken as the initial value whenscrambling/descrambling.

Also, in the event that the initial value when scrambling/descramblingis n bits in length (wherein n is a natural number), an arrangement maybe made wherein the number of logics “1” and the number of logics “0” inthe physical layer header section or a part thereof are countedrespectively, the absolute value of the difference thereof isrepresented with (n−i) bits in binary, an i-bit sequence such that atleast one bit thereof is logic “1”, shared with an other party ofcommunication is inserted in the extracted bit sequence of the (n−i)bits in a pattern shared with the other party of communication, therebygenerating the initial value when scrambling/descrambling.

Also, in the event that the initial value when scrambling/descramblingis n bits in length (wherein n is a natural number), an arrangement maybe made wherein the number of logics “1” and the number of logics “0” inthe physical layer header section or a part thereof are countedrespectively, the absolute value of the difference thereof is obtained,z shared with an other party of communication (wherein z is a naturalnumber smaller than 2^(n)) is added to the absolute value, the result isrepresented with z bits in binary, and this bit sequence is taken as theinitial value when scrambling/descrambling.

Now, with a wireless communication system according to the presentinvention, wireless transmission is basically performed in atransmission frame format made up of a physical layer header section anda data section, but the configuration of the transmission frame isunrestrained.

For example, a transmission frame is made up of one or more pairs of aphysical layer header section and a data section. In such a case, aninitial value when scrambling or descrambling is acquired from eachphysical layer header section, and by using an initial value extractedfrom a physical layer header section, scrambling or descrambling of thedata section to be coupled with the physical layer header section can beperformed.

In the event of including a non-scrambled signal between a physicallayer header section and a data section, the start position ofscrambling or descrambling of a data section should be delayed by apredetermined period corresponding to transmission and reception of anon-scrambled signal section following transmission or reception of aphysical layer header section. For example, this is transmitted as atraining signal for equalizing a transmission path, or a signal of whichdata to be subjected to broadcast to peripheral stations, or the likedoes not need scrambling.

Alternatively, a transmission frame sometimes includes two or morephysical layer header sections. In such a case, an initial value whenscrambling or descrambling is acquired from each physical layer headersection, and scrambling or descrambling of the subsequent signals shouldbe performed using the initial value extracted from each physical layerheader section. That is to say, following the next physical layer headersection appearing until an initial value when scrambling or descramblingis newly acquired, scrambling or descrambling of the subsequent signalscontinuously should be performed using the initial value when scramblingor descrambling, which has been acquired last.

Also, with a wireless communication system for performing space-divisionmultiplexing communication, a transmission frame is provided with eachphysical layer header section subjected to time division multiplexingcorresponding to the data section over each channel subjected tospace-division multiplexing. In such a case, scrambling or descramblingof the data section to be transmitted over the corresponding channelshould be performed using the initial value extracted from each physicallayer header section.

Also, according to a second aspect of the present invention, a computerprogram which is described in a computer-readable format so as toexecute control of communication operation of transmission data made upof a physical layer header section and a data section on a computersystem, the program comprising:

a scrambling/descrambling initial-value generating step for generatingan initial value when scrambling or descrambling using at least a partof a physical layer header section based on a rule common with an otherparty of communication; and

a scrambling/descrambling step for performing scrambling or descramblingof a data section using the initial value.

The computer program according to the second aspect of the presentinvention is defined as a computer program which is described in acomputer-readable format so as to realize predetermined processing on acomputer system. In other words, by installing the computer programaccording to the second aspect of the present invention on a computersystem, collaborative operation is exhibited on the computer system,which operates as a wireless communication apparatus. A wireless networkis established by activating a plurality of such wireless communicationapparatuses, whereby the same advantages as the wireless communicationsystem according to the first aspect of the present invention can beobtained.

Advantage

According to the present invention, synchronization between a scramblerand a descrambler can be realized with high error tolerance in acommunication system.

Also, according to the present invention, an excellent wirelesscommunication system, wireless communication apparatus and wirelesscommunication method, and computer program can be provided wherein ascrambling initial value can be shared between transmission andreception without deteriorating transmission efficiency of user datawhich a user actually wants to send.

Also, according to the present invention, there is no need to provide adedicated field for notifying the initial value of scrambling within atransmission data frame, thereby contributing to improvement of datatransmission efficiency.

Also, according to the present invention, a value equivalent to ascrambling initial value can be transmitted with a field which canemploy a modulation method and encoding rate having less required S/N,i.e., a physical header, so while the transmission error of a scramblinginitial value is reduced, the number of transmission bits of a fieldemploying a modulation method and encoding rate having higher requiredS/N can be reduced by the amount of the above reduction, andaccordingly, transmission errors can be reduced on the whole, therebycontributing to improvement of transmission efficiency from thisperspective as well.

Specifically, for example, let us consider when under AWGN, and SNR=12[dB]. In order to facilitate description, let us consider that biterrors occur independently at random, and let us set up an error rate atthis time as the following. Note that this value is a realistic valueapproximated using a computer simulation. Now, let us say that the sizeof DATA is 100 bytes.

SNR=12 [dB] BPSK R=½ BER: 0 (absolutely no error)

SNR=12 [dB] 16QAM R=½ BER: 1.0e⁻⁴

With a conventional method, if the SIGNAL section (24 bits) istransmitted by BPSK R=½, and the Service+DATA section (816 bits) istransmitted by 16QAM R=½, error-free probability on the whole is(1−0)²⁴×(1−10e⁻⁴)⁸¹⁶=0.9216. On the other hand, according to the presentinvention, if the SIGNAL section (24 bits) is transmitted by BPSK R=½,and the Service+DATA section (800 bits) is transmitted by 16QAM R=½,error-free probability on the whole is (1−0)²⁴×(1−10⁻⁴)⁸⁰⁰=0.9231.Accordingly, it can be understood that according to the presentinvention, error-free probability improves, which contributes toimprovement of throughput on the whole system.

Also, the present invention employs a scrambling notification method,which is closed only for a PHY layer without depending on upper layerformats, so can handle the format of a wide-range communication system.

The other objects, characteristics, and advantages regarding the presentinvention will be apparent with more detailed description based onlater-described embodiment of the present invention and the appendeddrawings.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, description will be made in detail regarding an embodimentof the present invention with reference to the drawings.

FIG. 1 schematically illustrates the entire configuration of acommunication system according to an embodiment of the presentinvention. With the example in the drawing, a communication apparatus 21to be connected to a network 30, and a communication apparatus 11 to beconnected to a information processing device 12 are connected bywireless. The communication apparatus 21 serves as an access point (AP),and controls connection to the network 30 from another communicationapparatus. The communication apparatus 11 serves as a terminal, andattempts, for example, connection to the network 30 by communicatingwith the communication apparatus 21. This communication apparatus 11 canbe connected with, for example, a personal computer or the like as ainformation processing device 12. The communication apparatus 21,communication apparatus 11, and network 30 forms a wireless LAN (LocalArea Network) serving as another network.

Hereinafter, description will be made regarding the configuration of thecommunication apparatus 11. The communication apparatus 11 andcommunication apparatus 21 have basically the same internalconfiguration, though each serves differently.

A. Configuration and Operation of Wireless Communication Apparatuses

FIG. 2 schematically illustrates the functional configuration of atransmitter according to an embodiment of the present invention.

In the event of data communication such as connected to a computer, adata signal is input to an input/output processing unit 502, and isconverted into an appropriate digital data sequence.

Subsequently, a transmission data processing unit 510 inputs thetransmission data sequence, and receives communication control data tobe transmitted to a wireless communication apparatus serving as a otherparty of wireless communication (not shown) from a control unit 504 ifnecessary, and forms and outputs frame and slot configurations to betransmitted in a wireless zone following the communication control databeing multiplexed as appropriate.

Subsequently, a CRC adder 512 adds redundancy for detecting an error onthe reception side to the transmission data, and further a cipher device514 subjects the transmission data to encryption, and outputs this.

Subsequently, a scrambler 516 subjects the transmission data toscrambling so as to form pseudo-random in accordance with apredetermined algorithm. Also, a header generating unit 517 generates aPHY header. The scrambler 516 generates a scrambling initial value usinga part of bits of the PHY header generated by the header generating unit517, but the description thereof will be made later in detail.

Note that with the IEEE802.11a standard, the following generatorpolynomial is stipulated.S(x)=x ⁷ +x ⁴+1

Subsequently, a encoder 518 subjects the transmission data to the PHYheader and convolution encoding, and then an interleaver 520 subjectsthe transmission data to interleaving. According to this interleavingprocessing, the coded bit sequence is rearranged in accordance with aparticular rule, so on the reception side, a burst error can beconverted into a random error by performing the inverse operationthereof, i.e., de-interleaving.

Subsequently, a modulator 522 subjects the transmission data to mappingto signal points at the time of transmission, and outputs inphasecomponents (I components) and orthogonal components (Q components). TheOFDM modulation is performed by a complex IFFT unit 524 subjecting theoutput thereof to inverse FFT.

Subsequently, a time-waveform trimming unit 526 provides guard time byadding a cycle prefix, and subjects the transmission data to window wingprocessing so as to smooth the rise and decay of the OFDM modulationsymbol.

Subsequently, a DA converter 528 converts the transmission data from adigital waveform to an analog waveform, and further an RF transmitter530 subjects the transmission data to filtering, vector modulation usingthe I components and Q components, a frequency conversion to anappropriate transmission frequency channel, control of transmissionpower, amplification, and so forth.

The transmission signal up-converted by the RF transmitter 530 is inputto an antenna 534 via an antenna duplexer 532, and finally transmittedfrom the antenna 134 as an electromagnetic wave. This transmissionsignal is received by a other party of wireless communication (notshown).

Note that the antenna duplexer 534 is used for separating a transmissionsignal and a reception signal, an antenna switch is employed in the TDDmethod and the FDD/TDMA method, and a duplexer is generally employed inthe other methods. Now, let us say that an antenna switch is employedbecause IEEE802.11a of the TDD method is employed as an example.

Each unit of the transmission system is connected to the control unit504 via a transmission system control line 508. Accordingly, the controlunit 504 can perform various operation control and monitoring of thetransmission system such as on/off control of the transmission system,operation control and status monitoring of the RF transmitter 530, fineadjustment of transmission timing, modification of an encoding method orsignal point mapping method, control of retransmission, and the like viathe transmission system control line 508.

Also, FIG. 3 schematically illustrates the functional configuration of areceiver according to an embodiment of the present invention.

The transmission signal from the other party of wireless communicationis received at an antenna 634 as an electromagnetic wave. The signal isseparated from the own transmission signal at an antenna duplexer 632,following which is input to an RF receiver 640. The RF receiver 640subjects the reception signal to amplification, attenuation ofunnecessary frequency components, selection of a desired frequencychannel, frequency conversion, reception signal amplitude level control,vector detection process for separating the I components and the Qcomponents, band limit, and the like, and thus the I components and theQ components of the reception signal are extracted.

An AD converter 642 converts the reception signal down-converted by theRF receiver 640 from an analog waveform to a digital waveform.Subsequently, a synchronization circuit 644 subjects the reception datato frame synchronization, frequency error correction, and the like. Now,in the event of searching a communicable communication other partyimmediately after the power turns on or the like, detection of asynchronous signal or initial synchronization is performed using thissynchronization circuit 644. Various arrangements have been proposedregarding initial synchronization, frame synchronization, frequencyerror correction, and the like, but these are not directly associatedwith the essence of the present invention, so further description willnot be made in the present specification.

Subsequently, a time-waveform trimming unit 646 subjects the receptiondata to time waveform trimming so as to remove guard time provided byadding a cycle prefix, following which a complex FFT unit 648 subjectsthe reception data to FFT to perform the OFDM demodulation.

Subsequently, an equalizer 650 performs equalization using estimation ofa transmission path and estimation results. In some cases, the equalizer650 inputs the information of the synchronization circuit 644, and usesthis for estimation of a transmission path, or the like. Note thatvarious arrangements have been proposed as an equalizer, but these arenot directly associated with the essence of the present invention, sofurther description will not be made in the present specification.

The output of the equalizer 650 is input to a demodulator 652, and issubjected to signal point determination to output a reception bitestimation value. Subsequently, the reception data is input to ade-interleaver 654, and is subjected to de-interleaving for rearrangingthe coded bit sequence in accordance with a particular rule.Subsequently, a decoder 656 performs decoding of error correction codessubjected on the transmission side.

Subsequently, a descrambler 658 subjects the decoded reception data todescrambling, which is inverse conversion of scrambling performed on thetransmission side. Also, a header extractor 657 extracts a PHY headerfrom the decoded reception data. The descrambler 658 can yield the samescrambling initial value as the transmitter using a part of the PHYheader, but the description thereof will be made later. Note that withthe IEEE802.11a standard, the same type of a circuit as the scrambler isemployed as the descrambler.

Further, a decipher device 660 deciphers encryption subjected on thetransmission side, following which a CRC checking unit 662 outputs thereception data of which a CRC is removed, and the result of a CRC checkregarding the reception block.

Subsequently, in the event that determination is made that the result ofthe CRC check of the reception block has no error, a reception dataprocessing unit 664 removes the frame configuration and slotconfiguration subjected for transmission in a wireless zone.Subsequently, in the event of data communication such as connected witha computer, a data input/output processing unit 602 converts thereception data into a data signal, and outputs this.

In the event that the reception data includes communication control datatransmitted from the other party of wireless communication (not shown),that portion is extracted by the reception data processing unit 664, andis input to the control unit 604 via a reception system control line606. Subsequently, the control unit 604 interprets the received controldata, and performs operation control of each unit within a wirelesscommunication apparatus 600 in accordance with the received instruction.

Each unit of the reception system is connected to the control unit 104via the reception system control line 106. Accordingly, the control unit104 can perform various operation control and monitoring of thereception system such as on/off control of the reception system,operation control and status monitoring of the RF receiver 140, fineadjustment of reception timing, modification of an decoding method orsignal point mapping method, control of retransmission, and the like viathe reception system control line 106.

The present invention is characterized by a method for sharing ascrambling initial value between the transmission side and the receptionside. Now, description will be made in detail regarding handling ofscrambling and descrambling initial values on the transmission side withreference to FIG. 4 illustrating the configuration of around thescrambler 516 on the transmission side.

Data for generating a header made up of parameters for controlling aphysical layer such as an encoding rate is input to the header generator517 from the control unit 504. The encoder 518 subjects headerinformation generated here to error correction encoding. Following thisheader information subjected to error correction encoding being created,the transmission data subjected to error correction encoding is linkedthereto using a method such as described below.

That is to say, the transmission data is ciphered at the cipher device514, following which is scrambled by calculating an exclusive-ORoperation between the transmission data and a scrambling pattern to begenerated with a later-described method at the EXOR 516b within thescrambler 516. The encoder 518 subjects the output thereof to errorcorrection encoding to create the transmission data subjected to errorcorrection encoding.

On the other hand, the header generator 517 creates header informationbased oh the data for generating a header input from the control unit504, and outputs this to the encoder 518 and the scrambler 516. Ascrambling initial-value generator 516 c included in the scrambler 516generates a scrambling initial value from this header information usingany one of later-described various techniques. The scrambling initialvalue generated is input to a scrambling pattern generator 516 a. Infact, the scrambling pattern generator 516 a is also a scrambler made upof a shift register such as shown in FIG. 37, the scrambling initialvalue is set within this register, and a scrambling pattern is generatedby the values within the register being shifted in order for each clock.

Here, an example has been shown such that the data for generating aheader is once input to the header generator 517 from the control unit504, where header information is generated, and this is input not onlyto the encoder 518 but also to the scrambling generator 516 c, for thesake of facilitating description, but the essence of the presentinvention is not restricted to this. For example, an arrangement may bemade wherein the scrambling initial-value generating unit 516 c directlyreceives the data for generating a header from the control unit 504,creates header information with the same processing as the headergenerator 517 based on that, and then a scrambling initial value iscreated from the header information.

Also, FIG. 5 illustrates the configuration of around the descrambler 658on the reception side. Following the decoder 656 subjecting thereception data to error correction decoding, the reception data isdescrambled by calculating an exclusive-OR operation between thereception data and a descrambling pattern to be generated with alater-described method at an EXOR 658 b within the descrambler 658. Theoutput thereof is deciphered at the decipher device 660. In advance ofstarting descrambling, operation such as the following is performed toyield a descrambling initial value.

That is to say, following the decoder 656 subjecting the headerinformation not scrambled of the reception data to error correctiondecoding, the parameters for controlling a physical layer is extractedfrom the header information at the header extractor 657, and at the sametime, is input to the descrambling initial-value generator 658 c withinthe descrambler 658. Here, the descrambling initial-value generator 658c generates a descrambling initial value from the input headerinformation using any one of later-described various techniques. Thegenerated descrambling initial value is input to the descramblingpattern generator 658 a. In fact, the descrambling pattern generator 658a is also a descrambler made up of a shift register such as shown inFIG. 38, this descrambling initial value is set in this register, and adescrambling pattern is generated by the values within the registerbeing shifted in order for each clock.

FIG. 6 illustrates the internal configuration of a scrambler accordingto an embodiment of the present invention. A scrambler 220 shown in thedrawing comprises two shift registers 224 and 225, and two exclusive-ORcircuits 226 and 227, as the basic configuration of a scrambler. Theshift registers 224 and 225 make up a 7-bit shift register inconjunction, and hold an internal state as a scrambler. With these shiftregisters 224 and 225, the output at the 4th stage (X⁴) and the outputat the 7th stage (X⁷) are input to the exclusive-OR circuit 226. Also, asignal to be scrambled is input to one of the input ports of theexclusive-OR circuit 227. In the event of a normal scrambler, scramblingis performed by the output of the exclusive-OR circuit 226 beingsupplied to the other input port of the exclusive-OR circuit 227 and theinput of the shift register 224.

With this scrambler 220, an arrangement is made wherein a selector 223is provided between the output of the exclusive-OR circuit 226, one ofthe input ports of the exclusive-OR circuit 227, and the input of theshift register 224, and any one of the output port of the exclusive-OR226 and the output of the shift register 222 is connected to one of theinput ports of the exclusive-OR circuit 227 and the input of the shiftregister 224. Here, the shift register 222 is for holding the initialvalues of the shift registers 224 and 225. For example, a predetermined7 bits of a signal 620 can be employed as this initial value. This isbecause the signal 620 is transmitted with a modulation mode having higherror tolerance such as BPSK of encoding rate ½, so error-free receptioncan be expected at the reception device. In particular, in the event ofusing the lower 7 bits of data length 623, different values are assumedto be set for each packet, which is more preferable.

The control unit 221 provides timing control to the selector 223. Thecontrol unit 221 switches the selector 223 such that the output of theshift register 222 is supplied to one of the input ports of theexclusive-OR circuit 227 and the input of the shift register 224 at thetiming of a scrambler initialization 651 of a service 650 passingthrough the exclusive-OR circuit 227. Thus, the value held in the shiftregister 222 is set as the initial values of the shift registers 224 and225. Also, the scrambler initialization 651 is 7 bits of “0”, so thevalue held in the shift register 222 is output from the exclusive-ORcircuit 227 without any change due to the properties of the exclusive-ORcircuit. Subsequently, following the scrambler initialization 651passing through the exclusive-OR circuit 227, the control unit 221switches the selector 223 such that the output of the exclusive-ORcircuit 226 is supplied to one of the input ports of the exclusive-ORcircuit 227 and the input of the shift register 224.

Also, the control unit 221 refers to an initial-value setting flag 211,and in the event that the initial-value setting flag 211 indicates thatinitial value setting for the scrambler 220 is not performed, thecontrol unit 221 does not perform timing control in sync with the abovescrambler initialization 651, and controls the selector 223 such thatthe output of the exclusive-OR circuit 226 is always supplied to one ofthe input ports of the exclusive-OR circuit 227 and the input of theshift register 224. In this case, the values held in the exclusive-ORcircuits 226 and 227 are employed as a scrambler initial value withoutany change, and the scrambler initial value is output from theexclusive-OR circuit 227 without any change at the timing of thescrambler initialization 651 passing through the exclusive-OR circuit227.

Accordingly, even in the event that any state is selected at theselector 223, the scrambler initial value is output at the timing of thescrambler initialization 651 passing through the exclusive-OR circuit227, so it can be understood that this does not perform operationagainst the original IEEE802.11a standard.

FIG. 7 illustrates the configuration of a descrambler according to anembodiment of the present invention. A descrambler 270 shown in thedrawing comprises, as with the scrambler 220, two shift registers 274and 275, and two exclusive-OR circuits 276 and 277, as the basicconfiguration of a descrambler. The shift registers 274 and 275 make upa 7-bit shift register in conjunction, and hold an internal state as adescrambler. With these shift registers 274 and 275, the output at the4th stage (X⁴) and the output at the 7th stage (X⁷) are input to theexclusive-OR circuit 276. Also, a signal to be descrambled is input toone of the input ports of the exclusive-OR circuit 277. Further, thedescrambler 270 comprises a selector 273. In the event of a normaldescrambler, descrambling is performed by switching the selector 273such that the signal to be descrambled is supplied to one of the inputports of the exclusive-OR circuit 277 and the input of the shiftregister 274 at the timing of a signal equivalent to the scramblerinitialization 651 passing through the exclusive-OR circuit 277, andswitching the selector 223 such that the output of the exclusive-ORcircuit 276 is supplied to one of the input ports of the exclusive-ORcircuit 277 and the input of the shift register 274.

With this descrambler 270, a shift register 272 is provided, and theoutput of this shift register 272 is connected to the input of theselector 273. Here, the shift register 272 is for holding the initialvalues of the shift registers 274 and 275. As for these initial values,for example, a predetermined 7 bits of the signal 620 is available, butit is necessary for between the transmission device and the receptiondevice to determine regarding which bit position is used as a initialvalue beforehand.

The control unit 271 provides timing control to the selector 273. Thecontrol unit 271 switches the selector 273 such that the output of theshift register 272 is supplied to one of the input ports of theexclusive-OR circuit 277 and the input of the shift register 274 at thetiming of a signal equivalent to the scrambler initialization 651 of theservice 650 passing through the exclusive-OR circuit 277. Thus, thevalue held in the shift register 272 is set as the initial values of theshift registers 274 and 275. Subsequently, following the signalequivalent to the scrambler initialization 651 passing through theexclusive-OR circuit 277, the control unit 271 switches the selector 223such that the output of the exclusive-OR circuit 276 is supplied to oneof the input ports of the exclusive-OR circuit 277 and the input of theshift register 274.

Also, in the event that the control unit 221 obtains information thatsetting an initial value to the descrambler is not performed, thecontrol unit 221 does not select the value held in the shift register272, and switches the selector 273 such that the signal to bedescrambled is supplied to one of the input ports of the exclusive-ORcircuit 277 and the input of the shift register 274 at the timing of thesignal equivalent to the scrambler initialization 651 passing throughthe exclusive-OR circuit 277. As for the information that setting aninitial value is not performed, for example, a parity bit 624 of thesignal 620 is available. That is to say, in the event that the initialvalue is set to the scrambler at the transmission device, an odd parityis applied to the parity bit 624 by inverting an even parity when theheader generating unit 210 generates the parity bit 624. Thus,determination can be made regarding whether or not the initial value isset to the scrambler, i.e., regarding whether or not setting the initialvalue to the descrambler should be performed by checking this parity bit624 at the reception device.

Thus, by employing predetermined data of the signal 620 having higherror tolerance as the initial value of the descrambler, even if anerror occurs in signals equivalent to the scrambler initialization 651,descrambling can be performed normally.

Note that FIG. 4 and FIG. 5 focus on the explanations of operation ofthe scrambler and operation of the descrambler, which are characteristicwith the present invention, and for the sake of facilitating thedrawings, control lines for connection timing between the control unitand each unit, and on/off control such as shown in FIG. 2 and FIG. 3 areomitted.

Thus, according to the present invention, a scrambling initial value anda descrambling initial value are obtained based on header information,so there is no need to provide a field for notifying the scramblinginitial value within a transmission frame, thereby improving datatransmission efficiency. Also, the entire data section following theheader information can be scrambled, so concealment at the data sectioncan be assured, and also a biased distribution of “0” and “1” within thedata can be prevented.

Next, description will be made regarding communication operationaccording to an embodiment of the present invention with reference tothe drawings.

FIG. 8 illustrates the scrambling procedures in the transmission deviceaccording to an embodiment of the present invention using a flowchartformat.

First, upon an MAC frame being received from a communication controlunit 300, with a base-band processing unit 200, the header generatingunit 210 generates a PLCP header (Step S911).

In the event that the initial-value setting flag 211 indicates that aninitial value is not set to the scrambler (Step S912), the even parityof the signal 620 is generated in accordance with the IEEE802.11astandard to set this to the parity bit 624 (Step S913). Subsequently,the values held in the shift registers 224 and 225 within the scrambler220 are used as an internal state without any change (Step S914) toperform scrambling (Step S917).

On the other hand, in the event that the initial-value setting flag 211indicates that an initial value should be set to the scrambler (StepS912), the odd parity of the signal 620 is generated, or the even parityis generated and inverted to set this to the parity bit 624 (Step S915).Subsequently, the value held in the shift register 222 is set as aninitial value to the shift registers 224 and 225 which hold the internalstate within the scrambler 220 (Step S916) to perform scrambling (StepS917).

FIG. 9 illustrates the descrambling procedures in the reception deviceaccording to an embodiment of the present invention using a flowchartformat.

First, upon a convolution-code decoder 260 decoding a reception packet,a header analyzing unit 280 analyzes the PLCP header (Step S921).Subsequently, the header analyzing unit 280 checks regarding whether ornot the parity bit 624 in the signal 620 is the even parity conformingto the IEEE802.11a standard (Step S922).

In Step S922, in the event that determination is made that the paritybit 624 is the even parity conforming to the IEEE802.11a standard, thecontrol unit 271 switches the selector 273 such that the signal to bedescrambled is supplied to one of the input ports of the exclusive-ORcircuit 277 and the input of the shift register 274 as an initial valuein accordance with the standard at the timing of the signal equivalentto the scrambler initialization 651 passing through the exclusive-ORcircuit 277 (Step S924). Subsequently, following the signal equivalentto the scrambler initialization 651 passing through the exclusive-ORcircuit 277, the control unit 271 switches the selector 223 such thatthe output of the exclusive-OR circuit 276 is supplied to one of theinput ports of the exclusive-OR circuit 277 and the input of the shiftregister 274, and descrambling is performed (Step S927).

On the other hand, in Step S922, in the event that determination is madethat the parity bit 624 is the odd parity, the control unit 271 switchesthe selector 273 such that the output of the shift register 272 issupplied to one of the input ports of the exclusive-OR circuit 277 andthe input of the shift register 274 at the timing of the signalequivalent to the scrambler initialization 651 passing through theexclusive-OR circuit 277 to set an initial value (Step S926).Subsequently, following the signal equivalent to the scramblerinitialization 651 passing through the exclusive-OR circuit 277, thecontrol unit 271 switches the selector 223 such that the output of theexclusive-OR circuit 276 is supplied to one of the input ports of theexclusive-OR circuit 277 and the input of the shift register 274 anddescrambling is performed (Step S927). Note that in this case, in theevent of referring to the parity bit 624 at the subsequent processing,the odd parity is preferably changed to the even parity at this stage.

Thus, according to the present embodiment, synchronization between thescrambler 220 and the descrambler 270 can be realized with higher errortolerance by using a part of the signal 620 having high error toleranceas the initial value of the internal state of the scrambler 220. Also,the initial value of the descrambler 270 in the reception device can beappropriately selected by including that setting of an initial value isperformed in a part of the signal 620, and transmitting this to thescrambler 220.

Note that the communication system according to the present embodimentdoes not perform operation violating the rules on the specifications. Atthe timing of transmission of the signal equivalent to the scramblerinitialization 651, the initial value to be set as the internal state ofthe descrambler 270 is transmitted, thereby assuring operation inaccordance with the specifications. Also, even in the event that acommunication apparatus other than communication parties concernedreceives this signal, the reception packet is only discarded due to aparity error, so any defect exceeding this is not caused.

Next, description will be made regarding a modification example of theembodiment of the present invention with reference to the drawings.

FIG. 10 illustrates a first modification example of the embodiment ofthe present invention. With the first modification example shown in thedrawing, two types of the descramblers 270 and 290 are provided inparallel on the output side of the convolution-code decoder 260 in thereception device. The descrambler 270 is a descrambler such as shown inFIG. 6, and allows an initial value to be set using the shift register272. On the other hand, the descrambler 290 is a conventionaldescrambler such as shown in FIG. 11.

The basic configuration as a descrambler shown in FIG. 11 is the same asthe descrambler 270 shown in FIG. 5 in that two shift registers 294 and295, and two exclusive-OR circuits 296 and 297. A control unit 291switches a selector 293 such that a signal to be descrambled is suppliedto one of the input ports of the exclusive-OR circuit 297 and the inputof the shift register 294 at the timing of a signal equivalent to thescrambler initialization 651 of the service 650 passing through anexclusive-OR circuit 277. Subsequently, following the signal equivalentto the scrambler initialization 651 passing through the exclusive-ORcircuit 297, the control unit 291 switches the selector 293 such thatthe output of the exclusive-OR circuit 296 is supplied to one of theinput ports of the exclusive-OR circuit 297 and the input of the shiftregister 294.

In FIG. 10, an error determining unit 305 analyzes regarding whether ornot each field of the output of the descramblers 270 and 290 satisfiesthe range stipulated on the specifications. For example, with theexample shown in FIG. 35, following the SIGNAL field of the PHY header,the Service field of 16 bits continues, and of these 16 bits, 7 bitsfrom the MSB side are used for transmission of the initial value ofscrambling, and the residual 9 bits following these bits, serving asreserved bits, are stipulated to be set with all zeroes with the currentspecifications. Consequently, the descrambled result thereof must becomeall zeroes. Accordingly, the output of the descrambler indicating thatthese reserved bits are all zeroes is determined as reasonable output.

Also, as for the PSDU, the validity of the content thereof is supposedto be determined in light of correction ability of a block-code decoder320, but determination may be made using an error determining unit 305in a state prior to correction. For example, as shown in FIG. 12, theMAC header is appended to the MAC frame, which is the content of thePSDU, and each field of the MAC header includes predetermined data. Forexample, various types of control information are included in the framecontrol 710 of the headmost of the MAC header, and the protocol version711 of the headmost two bits thereof indicates the version of the MACprotocol. This protocol version 711 makes a rule of setting two bits ofthe value “0”, and the values other than this are reserved for thefuture use. Accordingly, in the event that this protocol versionincludes the value other than two bits of “0”, it can be determined thatthis cannot satisfy the range stipulated on the specifications. Notethat as for the determining method using the PSDU mentioned here, anarrangement may be made wherein determination is made using a signalfollowing the processing by the block-code decoder 320.

Similarly, as for the type 712 as well, two bits of the value “1” arereserved for the future use, so in the event that this type 712 includestwo bits of the value “1”, it can be determined that this cannot satisfythe range stipulated on the specifications. Also, as for the subsequentsubtype 713 as well, reserved bit patterns exist according to acombination with the type 712.

Accordingly, in the event that the initial value different from thescrambler 220 is set to any one of the descramblers 270 and 290, thereis the possibility that each field of the descrambled output cannotsatisfy the range stipulated on the specifications. The errordetermining unit 305 identifies such a field deviated from the rangestipulated on the specifications, and controls a selector 303 such thatof the descramblers 270 and 290, such output not deviated is supplied tothe block-code decoder 320. Note that delay units 307 and 309 are forholding the output of the scramblers 270 and 290 during a periodnecessary for determination at the error determining unit 305, and canbe realized with a delay line, shift register, and so forth.

For example, in the event that an initial value is not set to thescrambler 220 on the transmission device side, it can be conceived thatthe output of the descrambler 290 becomes correct, and the output of thedescrambler 270 becomes incorrect. This is because data sequencessubjected to descrambling with different initial values can be regardedas almost random, and it can be conceived that possibility to deviatethe range stipulated on the specifications is high. Also, in the eventthat an initial value is set to the scrambler 220 on the transmissiondevice side, the same initial value is set to the descramblers 270 and290 if an error does not occur. However, a signal equivalent to thescrambler initialization 651 is relatively low in error tolerance, thereis the possibility that an initial value to be set to the descrambler290 includes an error. In such a case, the output of the descrambler 270becomes correct, and the output of the descrambler 290 becomesincorrect, and accordingly, the error determining unit 305 performscontrol so as to select the output of the descrambler 270.

Thus, with the first modification example, an initial value can beselected by determination at the reception device side without notifyinginformation regarding setting of an initial value using the parity bit624 or the like by providing the descrambler 270 which takes a part ofthe signal 620 as an initial value, and the descrambler 290 which takesa signal equivalent to the scrambler initialization 651 as an initialvalue in parallel, and determining regarding whether or not each fieldof the output thereof satisfies the range stipulated on thespecifications.

FIG. 13 illustrates a second modification example of the embodiment ofthe present invention. With the second modification example shown in thedrawing, the two same-type descramblers 270 are provided in parallel onthe output side of the convolution-code decoder 260 in the receptiondevice. Let us say that these descramblers 270 take a part of the signal620 as an initial value respectively, but are mutually differentregarding which bit position is employed as an initial value. Forexample, if we say that two types of bit positions are stipulated on thetransmission side beforehand, and then the value of any one of the bitpositions is employed as an initial value depending on a radio wavestatus at the time of transmission, the two descramblers 270 are set soas to take the values of these two types of bit positions as initialvalues on the reception device side respectively, and then descramblingis performed.

The error determining unit 305 analyzes, as with the case of the abovefirst modification example, regarding whether or not each field of theoutput of the two descramblers 270 satisfies the range stipulated on thespecifications. Let us say that the two descramblers 270 performdescrambling with a different initial value respectively, so the outputthereof is also different. Accordingly, any one of the output of the twodescramblers 270 becomes correct, and the other output becomesincorrect, so the error determining unit 305 performs control so as toselect the output of the descramblers 270 which is correct on thespecifications.

Thus, with this second modification example, the two descramblers 270which take the value of a different bit position of the signal 620 as aninitial value respectively are provided in parallel, and determinationis made regarding whether or not the output of each field thereofsatisfies the range stipulated on the specifications, whereby the bitposition can be selected based on the determination of the transmissiondevice side, and an initial value can be selected based on thedetermination of the reception device side without notifying theinformation relating to the setting of an initial value using the paritybit 624 or the like.

Methods for Generating a Scrambling Initial Value and a DescramblingInitial Value

Hereinafter, description will be made regarding methods for generating ascrambling initial value and a descrambling initial value, which arecharacteristic portions with the present invention. Let us say that withthis description, physical layer header information such as shown inFIG. 14 is employed as header information. This is equivalent to theresidual obtained by removing the Service field from the physical layerheader of IEEE802.11a shown in FIG. 35. Also, let us say that anscrambling initial value and an descrambling initial value are each madeup of 7 bits.

Any one of later-described methods for generating a scrambling initialvalue and a descrambling initial value generates a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation. Accordingly, the Service field for notifying a scramblinginitial value, such as shown in FIG. 35, becomes unnecessary.Consequently, a user can use the 16 bits used for the Service field ofthe data section, thereby improving data transmission efficiency. Also,this allows the entire data section to be scrambled. However, theessence of the present invention is not restricted to the configurationshown in FIG. 5.

B-1. Method 1 for Generating a Scrambling Initial Value and aDescrambling Initial Value

FIG. 15 illustrates a first method for generating a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation.

This method utilizes that the SIGNAL field is not scrambled, extracts 7bits from a predetermined place within the SIGNAL field, set these tothe scrambler as an initial value for scrambling, and then scrambles andtransmits the Data section. With the example shown in FIG. 15, of theSIGNAL field, 7 bits are extracted from the MSB to the 7th bit in theLENGTH field, and these are employed as a scrambling initial value.

Also, following the SIGNAL field not scrambled being decoded, thereception side first extract 7 bits from a predetermined place of therelevant field in the same way, sets these to the descrambler as adescrambling initial value, and then starts descrambling of the DATAsection. With the example shown in FIG. 15, of the SIGNAL field, 7 bitsare extracted from the MSB to the 7th bit in the LENGTH field, and theseare employed as a scrambling initial value.

B-2. Method 2 for Generating a Scrambling Initial Value and aDescrambling Initial Value

In the event of generating a scrambling initial value using the abovegenerating method 1, unless a method for extracting 7 bits from thephysical header information is determined carefully, there is thepossibility that the 7 bits of that portion happen to be all zeroes,depending on the data contents. Even if all zero bits are employed as ascrambling initial value, this is output as the original data sequencewithout scrambling, so this is inappropriate for a scrambling initialvalue, which must be avoided.

Accordingly, in the event that a field which is assured not to be allzeroes exists in physical layer header information, a method can beconceived wherein both a transmitter and a receiver comply with theagreement such that the relevant bit field is included in 7 bits makingup a scrambling initial value.

For example, with IEEE802.11a, the RATE field serving as a placeindicating a modulation mode is provided in the physical headerinformation (see FIG. 14), and a method for describing the RATE field isstipulated such as shown in Table 1.

[Table 1]

According to Table 1, even if any specified transmission rate isselected between transmission and reception, it is assured that the RATEfield does not become all zeroes. Accordingly, if the same bitassignment as the RATE field is employed, the value obtained by mixingall values of this RATE field (4 bits) with the other field or a fixedvalue is taken as scrambling and descrambling initial values, whereby itcan be assured that these initial values do not become all zeroes.

FIG. 16 illustrates a second method for generating a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation. With the example shown in the drawing, of the SIGNAL field,4 bits of the RATE field, and subsequently, 3 bits from the MSB of theLENGTH field are extracted respectively, and the value obtained bylinking these bits is used as a scrambling initial value anddescrambling initial value. According to such a initial value, at least4 bits from the MSB of the 7 bits do not become all zeroes, so operationof the scrambler can be assured.

B-3. Method 3 for Generating a Scrambling Initial Value and aDescrambling Initial Value

As described with the above section B-2, all zeroes are inappropriatefor a scrambling initial value, which must be avoided. However, there isno guarantee that a field which does not become all zeroes alwaysexists, depending on the configuration of the physical layer headersection, a case can be conceived wherein a method for generating ascrambling initial value by linking bits extracted from a physical layerheader section cannot be used. As for a method for handling such a case,an example such as the following can be conceived.

That is to say, the transmission side extracts 7 bits from apredetermined place of the SIGNAL section, and performs scrambling usingthe extracted bits as a scrambling initial value in the event that theextracted bits are not all zeroes. On the other hand, in the event thatthe 7 bits extracted from the SIGNAL section happen to be all zeroes,let us say that the transmission side performs scrambling using acertain scrambling initial value of 7 bits (e.g., “0101111”) other thanall zeroes.

Similarly, the reception side first decodes the SIGNAL section notscrambled, extracts 7 bits from a predetermined place, and startsdescrambling using these as a descrambling initial value in the eventthat these are not all zeroes, but in the event that these happen to beall zeroes, the reception side determines that a certain scramblinginitial value of 7 bits (e.g., “0101111”) other than all zeroes is usedfor scrambling, and performs descrambling using this.

FIG. 17 illustrates a third method for generating a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation. With the example shown in the drawing, of the SIGNAL field,7 bits from the MSB of the LENGTH field are extracted, and employs theseas a scrambling initial value and a descrambling initial value in theevent that these are other than all zeroes. On the other hand, in theevent that the 7 bits extracted from the MSB of the LENGTH field happento be all zeroes, “0101111” which is provided beforehand is employed asa scrambling initial value and a descrambling initial value, therebypreventing the initial values from becoming all zeroes.

B-4. Method 4 for Generating a Scrambling Initial Value and aDescrambling Initial Value

As described with the above section B-2, all zeroes are inappropriatefor a scrambling initial value, which must be avoided, but there is noguarantee that a field which does not become all zeroes always exists,depending on the configuration of the physical layer header section, acase can be conceived wherein a method for generating a scramblinginitial value by linking bits extracted from a physical layer headersection cannot be used. As for a method for handling such a case, thoughthe method shown in the above section B-3 is available, with thissection, description will be made regarding the other method.

That is to say, in the event that a scrambling initial value is n bitsin length (wherein n is a natural number), the transmission sideextracts (n−k) bits from the physical layer header section or a partthereof based on a rule common between the transmission side and thereception side (wherein k is a natural number smaller than n), generatesa scrambling initial value by inserting a k-bit bit sequence knownbetween the transmission side and the reception side in the extractedbit sequence of the (n−k) bits in a pattern known between thetransmission side and the reception side, and then performs scramblingusing this scrambling initial value. Here, a bit sequence of which atleast one bit is logic “1” is employed for the known k bits to beinserted in the extracted bit sequence of the (n−k) bits, therebypreventing the initial value from becoming all zeroes.

Similarly, the reception side first decodes the SIGNAL section notscrambled, extracts (n−k) bits from the transmission data within thephysical layer header or a part thereof based on a rule commonly knownbetween the transmission side and the reception side, and inserts ak-bit sequence such as at least one bit thereof is logic “1” in theextracted bit sequence of the above (n−k) bits in a pattern knownbetween the transmission side and the reception side, and thus,generates a descrambling initial value, and consequently, restores thereception data sequence by performing descrambling.

Here, as long as k is a natural number satisfying 0<k<n, any value canbe assigned to k principally, but if a great value is assigned to k, thewidth of a value to be taken as a scrambling initial value narrows,which is not preferable. Accordingly, in order to assure of preventing ascrambling initial value from becoming all zeroes, the lowest limit k=1is preferable.

FIG. 18 illustrates a fourth method for generating a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation. With the example shown in the drawing, k=1 is assigned.With the example shown in the drawing, only 6 bits from the MSB of theLENGTH field within the SIGNAL field are extracted, these are employedfor 6 bits from the LSB side of a scrambling initial value, and theresidual one bit is employed for the MSB of the scrambling initial valueas the fixed value of 1, thereby preventing the scrambling initial valuefrom becoming all zeroes.

In the event of inserting such a fixed bit, the place of the fixed valueone bit of “1” does not need to be the MSB, so any bit position of theinitial value of 7 bits may be available. That is to say, both thetransmitter and the receiver should comply with the agreement forinserting the fixed value “1” in the same place at the stage of systemdesign, so the bit insertion position is not restricted to that shown inthe drawing.

B-5. Method 5 for Generating a Scrambling Initial Value and aDescrambling Initial Value

So far description has been made regarding the methods for generating ascrambling initial value based on the bit pattern extracted fromphysical layer header information, but methods other than those methodscan be conceived wherein a scrambling initial value is generated whilepreventing all zeroes based on physical layer header information.

As an example thereof, a method can be conceived wherein a scramblinginitial value is generated based on the number of logics “1” included inphysical layer header information. FIG. 19 illustrates a fifth methodfor generating a scrambling initial value and a descrambling initialvalue based on physical layer header information. The example shown inthe drawing illustrates a case wherein the Reserve field is taken aszero, and 100 bytes are transferred by BPSK R1/2.

In this case, the RATE field becomes “1101”, and the LENGTH fieldbecomes “001001100000”, and accordingly, so far the number of logics “1”in the bit fields is 6, and in the event of performing even parity, thePARITY field is set with “0”. Accordingly, the number of logics “1” onthe entire SIGNAL field is 6, and in the event of representing this with7 bits in binary, this becomes “0000110”. Let us say that this isemployed as the scrambling initial value, the transmitter side sets thisas the initial value of X¹ through X⁷ as described within the scramblerand descrambler of the top of FIG. 19, and performs scrambling.

Also, the reception side first decodes the SIGNAL section not scrambledin the same way, counts the number of logics “1” in the SIGNAL fieldfollowing decoding, and employs the value obtained by representing thenumber thereof with 7 bits in binary as the descrambling initial value.With the example shown in FIG. 19, the reception side sets “0000110” asthe initial value of X¹ through X⁷ as described within the scrambler anddescrambler, and starts descrambling.

Such as the embodiment shown in the drawing, in the event of employingbit assignment of the RATE field and the LENGTH field such as defined inIEEE802.11a, the number of logics “1” must be one or more, which is veryconvenient for using as scrambling initialization.

Incidentally, with the above description, the physical layer headerinformation similar to IEEE802.11a is assumed to be employed, the numberof logics “1” is not more than 24 even including the TAIL section whichmust be all zeroes. The initial value of the scrambler used here as anexample is 7-bit width, and accordingly, can handle the number of logics“1” up to 127, which is not miscarried. However, if the number of bitsof the physical layer header information is 127 or more, and in theevent that the scrambling initial value is 7-bit width, a problem iscaused wherein upon the number of logics “1” being simply counted withinthe entire physical layer header information, bit width comes short.

This problem can be handled with methods wherein in order to handle thisproblem, in the event of counting logic “1” within the physical layerheader, the number of logics “1” is counted only regarding apredetermined number of bit portions of 127 or less (defined commonlybetween the transmission side and the reception side) without employingthe entire portion, a value obtained by representing the counted resultin binary is employed as the scrambling initial value, or following thenumber of logics “1” of the entire portion being counted, the obtainednumber is divided by 2⁷=128 (here, 7th root is a value determined by thebit width of the scrambling/descrambling initial value), and then theremainder thereof is employed as the scrambling initial value, and thesemethods are also encompassed in the essence of the present invention.

B-6. Method 6 for Generating a Scrambling Initial Value and aDescrambling Initial Value

In the event of generating a scrambling initial value using a methodsuch as described in the above section B-5, a problem is not caused inthe event of assuring that the number of logics “1” does not become allzeroes by the definition of the physical header information, but if thisis not assured, there is the possibility that the scrambling initialvalue becomes all zeroes. To this end, description will be maderegarding a method for preventing all zeroes by expanding the rule ofgenerating a scrambling initial value in this section.

Let us determine that the number of logics “1” within physical layerheader information is counted, and in the event that the number is notzero, for example, a value obtained by representing the number thereofwith 7 bits in binary is taken as the scrambling initial value, andscrambling is performed, but in the event that the number of logics “1”happens to be zero, scrambling is performed using a certain scramblinginitial value of 7 bits (e.g., “0101111”) other than all zeroes.

Similarly, the reception side first decodes the physical layer headersection not scrambled, counts the number of logics “1” within thephysical layer header information, and in the event that the number isnot zero, takes a value obtained by representing the number thereof with7 bits in binary as the descrambling initial value, and startsdescrambling, but in the event that the number of logics “1” happens tobe zero, the reception side determines that scrambling is performedusing a certain scrambling initial value of 7 bits (e.g., “0101111”)other than all zeroes, and performs descrambling using this.

FIG. 20 illustrates a sixth method for generating a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation using an expanded rule for preventing all zeroes. With theexample shown in the drawing, the number of logics “1” of the SIGNALfield is counted, and in the event that the number thereof is not zero,scrambling is performed taking a value obtained by representing thenumber thereof with 7 bits in binary as the scrambling initial value. Onthe other hand, in the event that the number of logics “1” happens to beall zeroes, the initial value is prevented from becoming all zeroes byemploying previously provided “0101111” as the scrambling initial valueand the descrambling initial value.

B-7. Method 7 for Generating a Scrambling Initial Value and aDescrambling Initial Value

All zeroes are inappropriate for a scrambling initial value, whichshould be prevented, but depending on the configuration of the physicallayer header section, a case can be conceived wherein no field whichdoes not take all zeros exists, and accordingly the method forgenerating a scrambling initial value described at the above section B-5cannot be used. A method such as the method described with the previoussection B-6 is available as one of the methods for preventing this, butwith this section, description will be made regarding the other method.

That is to say, in the event that a scrambling initial value is n bitsin length (wherein n is a natural number), the transmission sidegenerates a scrambling initial value by counting the number of logics“1” included in the transmission data within a physical layer header ora part thereof, and inserting an m-bit bit sequence known between thetransmission side and the reception side in the bit sequence obtained byrepresenting the counted value with (n−m) bits (wherein m is a naturalnumber smaller than n) in binary in a pattern known between thetransmission side and the reception side, and then performs scramblingusing this scrambling initial value. Here, a bit sequence of which atleast one bit is logic “1” is employed for the m bits to be inserted inthe bit sequence of the (n−m) bits, thereby preventing the scramblinginitial value from becoming all zeroes.

Also, the reception side similarly counts the number of logics “1”included in the transmission data within the received physical layerheader or a part thereof, performs descrambling taking a value obtainedby inserting an m-bit bit sequence of which at least one bit is logic“1” known between the transmission side and the reception side in thebit sequence obtained by representing the counted value with (n−m) bitsin binary in a pattern known between the transmission side and thereception side as the descrambling initial value, and thus, restores thereception data.

Here, as long as m is a natural number satisfying 0<m<n, any value canbe assigned to m principally, but if a great value is assigned to m, thewidth of a value to be taken as a scrambling initial value narrows,which is not very preferable. Accordingly, in order to assure ofpreventing a scrambling initial value from becoming all zeroes, thelowest limit m=1 is preferable.

FIG. 21 illustrates a seventh method for generating a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation. With the example shown in the drawing, m=1 is assigned.With the example shown in the drawing, the number of logics “1” of thephysical layer header information is 6, “000110” obtained byrepresenting the number thereof with 6 bits in binary is employed as 6bits from the LSB side of the scrambling initial value, and the residualone bit is employed for the MSB of the scrambling initial value as thefixed value of 1.

In the event of inserting such a fixed bit, the place of the fixed value“1” of one bit may be any bit position of the initial value of 7 bits.That is to say, both the transmitter and the receiver should comply withthe agreement for inserting the fixed value “1” in the same place at thestage of system design, so the bit insertion position is not restrictedto that shown in the drawing.

B-8. Method 8 for Generating a Scrambling Initial Value and aDescrambling Initial Value

All zeroes are inappropriate for a scrambling initial value, whichshould be prevented, but depending on the configuration of the physicallayer header section, a case can be conceived wherein no field whichdoes not take all zeros exists, and accordingly the method forgenerating a scrambling initial value based on the bit sequenceextracted from the physical header section cannot be used (the same asabove). With this section, description will be made regarding the othermethod to prevent this problem.

That is to say, in the event that a scrambling initial value is n bitsin length (wherein n is a natural number), the transmission side countsthe number of logics “1” included in the transmission data within aphysical layer header or a part thereof, adds x commonly known betweenthe transmission side and the reception side (wherein x is a naturalnumber smaller than 2^(n)) to the counted number, and then performsscrambling taking a bit sequence obtained by representing the resultwith n bits in binary as the scrambling initial value.

Also, the reception side similarly counts the number of logics “1”included in the transmission data within the received physical layerheader or a part thereof, adds x commonly known between the transmissionside and the reception side (wherein x is a natural number smaller than2^(n)) to the counted number, and then performs descrambling taking abit sequence obtained by representing the result with n bits in binaryas the descrambling initial value, and thus, restores the receptiondata.

Here, if we say that the number of the total bits of the transmissiondata within the physical layer header is b0, and the bit width of thescrambling initial value and the descrambling initial value is s,satisfying b0+x≦2^(s) is preferable. Otherwise, there is the possibilitythat the generated scrambling initial value and descrambling initialvalue become all zero due to carryover of a digit.

In this case, let us say that the number of logics “1” is not countedregarding the entire bits of the transmission data within the physicallayer header, but the number of logics “1” is counted regarding a partthereof b1 (assuming that the place to be counted have been mutuallyunderstood between the transmission side and the reception side), and b1should be determined so as to satisfy b1+x≦2^(s). Alternatively, theabove case can be handled using a method wherein following the number oflogics “1” being counted regarding the entirety, x is added to this, theobtained number is divided by 2^(s), and then the reminder thereof isemployed as the scrambling initial value. These mentioned methods arealso encompassed in the scope of the essence the present invention.

Here, as long as x is a natural number satisfying 0<x<2^(n), any valuecan be assigned to x principally, but if a great value is assigned to x,the width of a value to be taken as a scrambling initial value narrows,which is not very preferable. Accordingly, in order to assure ofpreventing a scrambling initial value from becoming all zeroes, thelowest limit x=1 is preferable.

FIG. 22 illustrates an eighth method for generating a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation. With the example shown in the drawing, x=1 is assigned.With the example shown in the drawing, the number of logics “1” includedin the physical layer header information is 6, this value is added to“1” to obtain 7, 7 is represented with 7 bits width in binary to obtain“0000111”, and this “0000111” is taken as the scrambling initial value.

Also, the reception side can determine that the number of logics “1”included in the received physical layer header information is 6 in thesame way, so this value is added to “1” to obtain 7, 7 is representedwith 7 bits width in binary to obtain “0000111”, performs descramblingtaking this “0000111” as the descrambling initial value, andconsequently, restores the reception data.

B-9. Method 9 for Generating a Scrambling Initial Value and aDescrambling Initial Value

With the above section B-5, a scrambling initial value and adescrambling initial value are generated from the number of logics “1”,but inversely, a method for generating a scrambling initial value and adescrambling initial value using the number of logics “0” exists.

FIG. 23 illustrates a ninth method for generating a scrambling initialvalue and a descrambling initial value based on the number of logics “0”within the physical layer header information. The example shown in thedrawing illustrates a case wherein the Reserve field is zero, and 100bytes are transferred by BPSK R1/2.

In this case, the RATE field becomes “1101”, and the LENGTH fieldbecomes “001001100000”, so that so far the number of logics “1” in thebit fields is 6, and in the event of performing even parity, the PARITYfield is set to “0”. Accordingly, the number of logics “0” on the entireSIGNAL field is 18, and if this is represented with 7 bits in binary,this becomes “0010010”. Let us say that this is employed as thescrambling initial value, the transmitter side sets this as the initialvalue of X¹ through X⁷ as described within the scrambler and descramblerof the top of FIG. 23, and performs scrambling.

Also, the reception side first decodes the SIGNAL section not scrambledin the same way, counts the number of logics “0” in the SIGNAL fieldfollowing decoding, and employs the value obtained by representing thenumber thereof 18 with 7 bits in binary as the descrambling initialvalue. With the example shown in FIG. 23, the reception side sets“0010010” as the initial value of X¹ through X⁷ as described within thescrambler and descrambler, and starts descrambling.

Such as the embodiment shown in the drawing, in the event of employingbit assignment of the RATE field and the LENGTH field such as defined inIEEE802.11a, the number of logics “1” must be one or more, which is veryconvenient for using as scrambling initialization.

Incidentally, with the above description, the physical layer headerinformation similar to IEEE802.11a is assumed to be employed, the numberof logics “0” is not more than 24 even including the TAIL section whichmust be all zeroes. The initial value of the scrambler used here as anexample is 7-bit width, and accordingly, can handle the number of logics“0” up to 127, which is not miscarried. However, if the number of bitsof the physical layer header information is 127 or more, and in theevent that the scrambling initial value is 7-bit width, a problem iscaused wherein upon the number of logics “0” being simply counted withinthe entire physical layer header information, bit width comes short.

This problem can be handled with methods wherein in order to handle thisproblem, in the event of counting logic “0” within the physical layerheader, the number of logics “0” is counted only regarding apredetermined number of bit portions of 127 or less (defined commonlybetween the transmission side and the reception side) without employingthe entire portion, a value obtained by representing the counted resultin binary is employed as the scrambling initial value, or following thenumber of logics “0” of the entire portion being counted, the obtainednumber is divided by 2⁷=128 (here, 7th root is a value determined by thebit width of the scrambling/descrambling initial value), and then theremainder thereof is employed as the scrambling initial value, and thesemethods are also encompassed in the essence of the present invention.

B-10. Method 10 for Generating a Scrambling Initial Value and aDescrambling Initial Value

In the event of generating a scrambling initial value using a methodsuch as described with the above B-9, a problem is not caused in theevent of assuring that the number of logics “0” does not become allzeroes by the definition of the physical header information, but if thisis not assured, there is the possibility that the scrambling initialvalue becomes all zeroes. To this end, description will be maderegarding a method for preventing all zeroes by expanding the rule ofgenerating a scrambling initial value with this section.

Let us determine that the number of logics “0” within physical layerheader information is counted, and in the event that the number is notzero, for example, a value obtained by representing the number thereofwith 7 bits in binary is taken as the scrambling initial value, andscrambling is performed, but in the event that the number of logics “0”happens to be zero, scrambling is performed using a certain scramblinginitial value of 7 bits (e.g., “0101111”) other than all zeroes.

Similarly, the reception side first decodes the physical layer headersection not scrambled, counts the number of logics “0” within thephysical layer header information, and in the event that the number isnot zero, takes a value obtained by representing the number thereof with7 bits in binary as the descrambling initial value, and startsdescrambling, but in the event that the number of logics “0” happens tobe zero, the reception side determines that scrambling is performedusing a certain scrambling initial value of 7 bits (e.g., “0101111”)other than all zeroes, and performs descrambling using this.

FIG. 24 illustrates a tenth method for generating a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation using an expanded rule for preventing all zeroes. With theexample shown in the drawing, the number of logics “0” of the SIGNALfield is counted, and in the event that the number thereof is not zero,scrambling is performed taking a value obtained by representing thenumber thereof with 7 bits in binary as the scrambling initial value. Onthe other hand, in the event that the number of logics “0” happens to beall zeroes, the initial value is prevented from becoming all zeroes byemploying previously provided “0101111” as the scrambling initial valueand the descrambling initial value.

B-11. Method 11 for Generating a Scrambling Initial Value and aDescrambling Initial Value

All zeroes are inappropriate for a scrambling initial value, whichshould be prevented. However, depending on the configuration of aphysical layer header section, a case can be conceived wherein thenumber of logics “0” is not assured not to become zero, and accordinglythe method for generating a scrambling initial value described at theabove section B-9 cannot be used. A method such as the method describedwith the previous section B-10 is available as one of the methods forpreventing this, but with this section, description will be maderegarding another method.

That is to say, in the event that a scrambling initial value is n bitsin length (wherein n is a natural number), the transmission sidegenerates a scrambling initial value by counting the number of logics“0” included in the transmission data within a physical layer header ora part thereof, and inserting an h-bit sequence known between thetransmission side and the reception side in the bit sequence obtained byrepresenting the counted value with (n−h) bits (wherein h is a naturalnumber smaller than n) in binary in a pattern known between thetransmission side and the reception side, and then performs scramblingusing this scrambling initial value. Here, a bit sequence of which atleast one bit is logic “0” is employed for the h bits to be inserted inthe bit sequence of the (n−h) bits, thereby preventing the initial valuefrom becoming all zeroes.

Also, the reception side similarly counts the number of logics “1”included in the transmission data within the received physical layerheader or a part thereof, performs descrambling taking a value obtainedby inserting an m-bit sequence of which at least one bit is logic “1”known between the transmission side and the reception side in the bitsequence obtained by representing the counted value with (n−m) bits inbinary in a pattern known between the transmission side and thereception side as the descrambling initial value, and thus, restores thereception data.

Here, as long as h is a natural number satisfying 0<h<n, any value canbe assigned to h principally, but if a great value is assigned to h, thewidth of a value to be taken as a scrambling initial value narrows,which is not very preferable. Accordingly, in order to assure ofpreventing a scrambling initial value from becoming all zeroes, thelowest limit h=1 is preferable.

FIG. 25 illustrates an eleventh method for generating a scramblinginitial value and a descrambling initial value based on physical layerheader information. With the example shown in the drawing, h=1 isassigned. With the example shown in the drawing, the number of logics“0” of the physical layer header information is 18, “010010” obtained byrepresenting the number thereof with 6 bits in binary is employed as 6bits from the LSB side of the scrambling initial value, and the residualone bit is employed for the MSB of the scrambling initial value as thefixed value of 1.

In the event of inserting such a fixed bit, the place of the fixed value“1” of one bit may be any bit position of the initial value of 7 bits.That is to say, both the transmitter and the receiver should comply withthe agreement for inserting the fixed value “1” in the same place at thestage of system design, so the bit insertion position is not restrictedto that shown in the drawing.

B-12. Method 12 for Generating a Scrambling Initial Value and aDescrambling Initial Value

All zeroes are inappropriate for a scrambling initial value, whichshould be prevented. However, depending on the configuration of aphysical layer header section, a case can be conceived wherein thenumber of logics “0” is not assured not to become zero, and accordinglythe method for generating a scrambling initial value described at theabove section B-9 cannot be used (the same as above). With this section,description will be made regarding the other method to prevent thisproblem.

That is to say, in the event that a scrambling initial value is n bitsin length (wherein n is a natural number), the transmission side countsthe number of logics “0” included in the transmission data within aphysical layer header or a part thereof, adds y commonly known betweenthe transmission side and the reception side (wherein y is a naturalnumber smaller than 2^(n)) to the counted number, and then performsscrambling taking a bit sequence obtained by representing the resultwith n bits in binary as the scrambling initial value.

Also, the reception side similarly counts the number of logics “0”included in the transmission data within the received physical layerheader or a part thereof, adds y commonly known between the transmissionside and the reception side (wherein y is a natural number smaller than2^(n)) to the counted number, and then performs descrambling taking abit sequence obtained by representing the result with n bits in binaryas the descrambling initial value, and thus, restores the receptiondata.

Here, if we say that the number of the total bits of the transmissiondata within the physical layer header is b0, and the bit width of thescrambling initial value and the descrambling initial value is s,satisfying b0+y≦2^(s) is preferable. Otherwise, there is the possibilitythat the generated scrambling initial value and descrambling initialvalue become all zero due to carryover of a digit.

In this case, let us say that the number of logics “0” is not countedregarding the entire bits of the transmission data within the physicallayer header, but the number of logics “0” is counted regarding a partthereof b1 (assuming that the place to be counted have been mutuallyunderstood between the transmission side and the reception side), and b1should be determined so as to satisfy b1+y≦2^(s). Alternatively, theabove case can be handled using a method wherein following the number oflogics “0” being counted regarding the entirety, y is added to this, theobtained number is divided by 2^(s), and then the reminder thereof isemployed as the scrambling initial value. These mentioned methods arealso encompassed in the scope of the essence of the present invention.

Here, as long as y is a natural number satisfying 0<y<2^(n), any valuecan be assigned to y principally, but if a great value is assigned to y,the width of a value to be taken as a scrambling initial value narrows,which is not very preferable. Accordingly, in order to assure ofpreventing a scrambling initial value from becoming all zeroes, thelowest limit y=1 is preferable.

FIG. 26 illustrates a twelfth method for generating a scrambling initialvalue and a descrambling initial value based on physical layer headerinformation. With the example shown in the drawing, y=1 is assigned.With the example shown in the drawing, the number of logics “0” includedin the physical layer header information is 18, this value is added to“1” to obtain 19, 19 is represented with 7 bits width in binary toobtain “0010011”, and this “0010011” is taken as the scrambling initialvalue.

Also, the reception side can determine that the number of logics “0”included in the received physical layer header information is 18 in thesame way, so this value is added to “1” to obtain 19, 19 is representedwith 7 bits width in binary to obtain “0010011”, performs descramblingtaking this “0010011” as the descrambling initial value, andconsequently, restores the reception data.

B-13. Method 13 for Generating a Scrambling Initial Value and aDescrambling Initial Value

With the above section B-5, description has been made regarding themethod for generating a scrambling initial value based on the number oflogics “1” included in physical layer header information. Conversely,with the above section B-9, description has been made regarding themethod for generating a scrambling/descrambling initial value using thenumber of logics “0”.

According to a modification example of these methods for generating ascrambling/descrambling initial value, the transmission side counts thenumber of logics “1” and the number of logics “0” included in physicallayer header information respectively, further obtains the absolutevalue of the difference between these numbers, represents this with 7bits in binary equivalent to the bit length of scrambling anddescrambling initial values, and then generates a scrambling initialvalue.

Similarly, the reception side first decodes the physical layer headersection not scrambled, counts the number of logics “1” and the number oflogics “0” included in the physical layer header informationrespectively, further obtains the absolute value of the differencebetween these numbers, represents this with 7 bits in binary, generatesa descrambling initial value, and then starts descrambling.

B-14. Method 14 for Generating a Scrambling Initial Value and aDescrambling Initial Value

With the above section B-13, we have no problem in the event that thenumber of logics “1” and the number of logics “0” included in physicallayer header information are not equal, but in the event that thesevalues are equal, the scrambling initial value becomes all zeroes, soscrambling fails to work.

With the above sections B-6 and B-10, description has been maderegarding the methods for preventing all zeroes by expanding the rule ofgenerating a scrambling initial value. With this section as well,description will be made regarding a method for preventing all zeroesbased on the same rule expansion.

The transmission side counts the number of logics “1” and the number oflogics “0” included in physical layer header information respectively,and further obtains the absolute value of the difference between thesenumbers. In the event that the absolute value of the difference betweenthese numbers is not zero, the transmission side can generate ascrambling initial value by representing this with 7 bits in binaryequivalent to the bit length of a scrambling initial value. On the otherhand, in the event that the absolute value of the difference betweenthese numbers happens to be zero, let us determine that the transmissionside performs scrambling using a predetermined scrambling initial valueof 7 bits other than all zeroes (e.g., “0101111”).

Similarly, the reception side first decodes the physical layer headersection not scrambled, counts the number of logics “1” and the number oflogics “0” included in the physical layer header informationrespectively, and further obtains the absolute value of the differencebetween these numbers. In the event that the absolute value of thedifference between these numbers is not zero, the reception sidegenerates a descrambling initial value by representing this with 7 bitsin binary equivalent to the bit length of a descrambling initial value.On the other hand, in the event that the absolute value of thedifference between these numbers happens to be zero, the reception sidestarts descrambling using a predetermined descrambling initial value of7 bits other than all zeroes (e.g., “0101111”).

B-15. Method 15 for Generating a Scrambling Initial Value and aDescrambling Initial Value

With the above sections B-7 and B-11, the other methods for preventing ascrambling initial value from becoming all zeroes have been described.With this section as well, the same method for preventing all zeroeswill be described.

That is to say, in the event that a scrambling initial value is n bitsin length (wherein n is a natural number), the transmission side countsthe number of logics “1” and the number of logics “0” included in thetransmission data within a physical layer header or a part thereofrespectively, and obtains the absolute value of the difference of thesenumbers. The transmission side generates a scrambling initial value byinserting an i-bit bit sequence known between the transmission side andthe reception side in the bit sequence obtained by representing theabsolute value with (n−i) bits (however, let us say that i is a naturalnumber smaller than n) in binary in a pattern known between thetransmission side and the reception side, and then performs scramblingusing this scrambling initial value. Here, a bit sequence of which atleast one bit is logic “1” is employed for the i bits to be inserted inthe bit sequence of the (n−i) bits, thereby preventing the scramblinginitial value from becoming all zeroes.

Also, similarly, the reception side counts the number of logics “1” andthe number of logics “0” included in the transmission data within thereceived physical layer header or a part thereof respectively, andobtains the absolute value of the difference of these numbers. Thereception side generates a descrambling initial value by inserting ani-bit but sequence known between the transmission side and the receptionside such as at least one bit thereof is logic “1” in the bit sequenceobtained by representing the absolute value with (n−i) bits in binary ina pattern known between the transmission side and the reception side,performs descrambling using this descrambling initial value, and thenrestores the reception data.

Here, as long as i is a natural number satisfying 0<i<n, any value canbe assigned to i principally, but if a great value is assigned to i, thewidth of a value to be taken as a scrambling initial value narrows,which is not preferable. Accordingly, in order to assure of preventing ascrambling initial value from becoming all zeroes, the lowest limit i=1is preferable.

B-16. Method 16 for Generating a Scrambling Initial Value and aDescrambling Initial Value

With the above sections B-8 and B-12, further the other methods forpreventing a scrambling initial value from becoming all zeroes have beendescribed. With this section as well, the same method for preventing allzeroes will be described.

That is to say, in the event that a scrambling initial value is n bitsin length (wherein n is a natural number), the transmission side countsthe number of logics “1” and the number of logics “0” included in thetransmission data within a physical layer header or a part thereofrespectively, and obtains the absolute value of the difference of thesenumbers. The transmission side adds z commonly known between thetransmission side and the reception side (wherein z is a natural numbersmaller than 2^(n)) to the absolute value, and then performs scramblingtaking a bit sequence obtained by representing the result with n bits inbinary as the scrambling initial value.

Also, similarly, the reception side counts the number of logics “1” andthe number of logics “0” included in the transmission data within thereceived physical layer header or a part thereof respectively, andobtains the absolute value of the difference of these numbers. Thereception side adds z commonly known between the transmission side andthe reception side (wherein z is a natural number smaller than 2^(n)) tothe absolute value, performs descrambling taking a bit sequence obtainedby representing the result with n bits in binary as the descramblinginitial value, and restores the reception data.

Here, if we say that the number of the total bits of the transmissiondata within the physical layer header is b0, and the bit width of thescrambling initial value and the descrambling initial value is s,satisfying b0+z≦2^(s) is preferable. Otherwise, there is the possibilitythat the generated scrambling initial value and descrambling initialvalue become all zero due to carryover of a digit.

In this case, let us say that the number of logics “1” is not countedregarding the entire bits of the transmission data within the physicallayer header, but the number of logics “1” is counted regarding a partthereof b1 (assuming that the place to be counted have been mutuallyunderstood between the transmission side and the reception side), and b1should be determined so as to satisfy b1+z≦2^(s). Alternatively, theabove case can be handled using a method wherein following the number oflogics “1” being counted regarding the entirety, z is added to this, theobtained number is divided by 2^(s), and then the reminder thereof isemployed as the scrambling initial value. These mentioned methods arealso encompassed in the scope of the essence of the present invention.

Here, as long as z is a natural number satisfying 0<x<2^(n), any valuecan be assigned to z principally, but if a great value is assigned to z,the width of a value to be taken as a scrambling initial value narrows,which is not very preferable. Accordingly, in order to assure ofpreventing a scrambling initial value from becoming all zeroes, thelowest limit z=1 is preferable.

The above description has been made wherein scrambling is performedtaking the bit sequence generated from the physical layer headerinformation without any change as a scrambling initial value, and alsodescrambling is performed taking this as a descrambling initial value.However, the essence of the present invention is not restricted to this,a case wherein the transmission side generates a bit sequence, whichbecomes the base of a scrambling initial value, performs bit inversionof this bit sequence, and uses this as the scrambling initial value,also the reception side generates a bit sequence, which becomes the baseof a descrambling initial value, performs bit inversion of this bitsequence, and uses this as the descrambling initial value, isencompassed in the scope of the essence of the present invention, andcan yield the same advantages of the present invention.

For example, with the embodiment shown in FIG. 19, in the event ofgenerating a scrambling initial value by counting the number of logics“1” within physical layer header information, even an arrangement isencompassed in the technical range of the present invention wherein ifthe number of logics “1” is 6, not “0000110” obtained by representingthis number with 7 bits in binary but “1111001” obtained bybit-inverting “0000110” is employed as the scrambling initial value,which is apparent.

C. Scrambling/Descrambling Corresponding to a Transmission Frame Format

So far description has been made principally regarding the methods fortransmitting a scrambling initial value using a region not scrambledsuch as a physical layer header. However, with actual wirelesscommunication, a transmission frame format can be conceived whereinmultiple fields not scrambled exist within one wireless frame. In thissection, description will be made regarding a method for applying ascrambling/descrambling method according to the present invention tovarious transmission frame formats.

FIG. 27 illustrates a configuration example of a transmission framewherein multiple fields not scrambled exist within one wireless frame.With the example shown in the drawing, a transmission frame comprises apreamble, which is the head of the transmission frame, and subsequently,multiple pairs made up of a physical layer header section and a datasection. Each physical layer header section stores a scrambling initialvalue to be used for scrambling the subsequent data section, which makesup a pair therewith.

When transmitting such a transmission frame, the physical layer headersection is not scrambled, and the subsequent data section is scrambledusing the scrambling initial value extracted from the immediatelypreceding physical layer header section. Also, when receiving thetransmission frame, the descrambling initial value is extracted from thephysical layer header section not scrambled, and the scrambled datasection to be received immediately after the physical layer headersection is descrambled using this descrambling initial value.

With the example shown in FIG. 27, a transmission frame comprises apreamble (Preamble), and subsequently, a pair of a physical layer headersection (PHY header) 1 and a data section (DATA) 1, and a pair of aphysical layer header section (PHY header) 2 and a data section (DATA)2. Note that the data section may be a known signal sequence.

At the time of transmission, information bits S1 stored in the physicallayer header section (PHY header) 1 is taken as the scrambling initialvalue, and the data section (DATA) 1 immediately after the PHY header 1is scrambled therewith, and similarly, information bits S2 stored in thephysical layer header section (PHY header) 2 are taken as the scramblinginitial value, and the data section (DATA) 2 immediately after the PHYheader 2 is scrambled therewith. Also, at the time of reception, thephysical layer header section (PHY header) 1 not scrambled is received,the information bits S1 are extracted, and the data section (DATA) 1immediately after the PHY header 1 is descrambled taking the S1 as thedescrambling initial value, and similarly, the physical layer headersection (PHY header) 2 not scrambled is received, the information bitsS2 are extracted, and the data section (DATA) 2 immediately after thePHY header 2 is descrambled taking the S2 as the descrambling initialvalue.

Also, FIG. 28 illustrates another configuration example of atransmission frame wherein multiple fields not scrambled exist withinone wireless frame. With the example shown in the drawing, immediatelyafter a physical layer header section (PHY header), a signal unnecessaryfor scrambling such as a training signal for equalizing a transmissionpath, data for performing broadcast to peripheral stations, or the likecontinues, and further subsequently, a data section (DATA) to bescrambled continues.

In the event of such a transmission frame format, at the time oftransmission, the data section is scrambled from the head thereof usingthe scrambling initial value stored in the physical layer headersection. Also, at the time of reception, first, the physical layerheader section not scrambled is received, the descrambling initial valueis extracted therefrom, the data section received immediately after thesignal not scrambled is descrambled using this descrambling initialvalue.

In such a case, following the physical layer header section beingtransmitted or received, the start position of scrambling ordescrambling should be delayed by a predetermined period correspondingto the transmission or reception of the signal portion not scrambled.

Also, FIG. 29 illustrates an configuration example of a transmissionframe wherein two or more physical layer header sections are includedwithin one transmission frame, following which a data section continues.With the example shown in the drawing, each physical layer headersection stores a scrambling initial value employed for scrambling thesubsequent transmission signals, and at the time of transmission orreception, scrambling and descrambling is performed at multi-stages eachtime each physical layer header is passed through.

That is to say, at the time of transmission, information bits S1 storedin a physical layer header section (PHY header) 1 are taken as thescrambling initial value, and the subsequent signal, i.e., a physicallayer header section (PHY header) 2 is scrambled. Similarly, informationbits S2 stored in the physical layer header section (PHY header) 2 aretaken as the scrambling initial value, and the subsequent signal, i.e.,a data section (DATA) is scrambled.

Also, at the time of reception, the physical layer header section (PHYheader) 1 not scrambled is received, the information bits S1 areextracted therefrom, and the subsequent signal, i.e., the physical layerheader section (PHY header) 2 is descrambled taking the S1 as thedescrambling initial value. Next, the information bits S2 are extractedfrom the physical layer header (PHY header) 2 descrambled, and the datasection (DATA) 2 immediately after the PHY header 2 is descrambledtaking the S2 as the descrambling initial value this time.

Also, FIG. 30 illustrates a configuration example of a transmissionframe wherein a preamble at the head of the frame, following whichmultiple pairs each made up of a physical layer header section and adata section continue, as with FIG. 27. Here, the data section may be aknown signal sequence.

With the example shown in FIG. 27, using the scrambling/descramblinginitial value extracted from each physical layer header section eachdata section immediately thereafter is scrambled/descrambled. That is tosay, scrambling/descrambling is performed only at one stage.

Conversely, with the example shown in FIG. 30, two-stagescrambling/descrambling is performed. That is to say, as with theexample shown in FIG. 29, using the initial value extracted from eachphysical layer header section signals immediately thereafter isscrambled/descrambled.

Specifically, at the time of transmission, taking information bits S1stored in a physical layer header section (PHY header) 1 as thescrambling initial value, the signals following this are scrambled. Withthe example shown in the drawing, taking the S1 as the scramblinginitial value, a data section (DATA) 1 and a physical layer headersection (PHY header) 2 are similarly scrambled. Here, when the physicallayer header section (PHY header) 2 appears, information bits S2 areextracted therefrom as a new scrambling initial value, and hereinafter,taking the S2 as the scrambling initial value, a signal following this,i.e., data section (DATA) 2 is scrambled.

Also, at the time of reception, the physical layer header section (PHYheader) 1 not scrambled is received, the information bits S1 areextracted therefrom as the descrambling initial value, signals followingthis are descrambled. With the example shown in the drawing, taking theS1 as the descrambling initial value, the data (DATA) 1 and the physicallayer header section (PHY header) 2 are descrambled. Here, when thephysical layer header section (PHY header) 2 appears, the informationbits S2 are extracted therefrom as a new descrambling initial value, andhereinafter, taking the S2 as the scrambling initial value, a signalfollowing this, i.e., the data section (DATA) 2 is scrambled.

In this case, following the next physical layer header section appearinguntil a new initial value at the time of scrambling or descrambling isacquired, the subsequent signal is scrambled or descrambled using theinitial value at the time of scrambling or descrambling acquired lastcontinuously.

Incidentally, recently, the MIMO (Multi-Input Multi-Output)communication method has been under study wherein space-divisionmultiplexing, i.e., multiple transmission paths, which are logicallyindependent, are established by both the transmitter side and thereceiver side equipping multiple antenna devices. The MIMO communicationis a technique for realizing expansion of transmission capacity, andachieving improvement in communication speed, employs space-divisionmultiplexing, and accordingly, excels in frequency use efficiency.

FIG. 31 illustrates a configuration example of a transmission frameformat which can be employed with the MIMO communication method. Withthe example shown in the drawing, four MIMO channels exist for datatransmission destinations, which supposes that four pieces of data aresubjected to space-division multiplexing and transmitted.

As shown in the drawing, with a transmission frame, following a preamble(Preamble), a physical layer header section (PHY header) 1 regarding theentire relevant transmission frame continues, further physical layerheader sections (PHY headers) 2 through 5 for each MIMO channel continueusing time division multiplexing, further subsequently, four datasections (DATA) 2 through 5 subjected to space-division multiplexingcontinue. Each data section can be assigned with each differenttransmission rate. For example, the data sections (DATA) 2 through 5 areassigned with 6 mbps, 6 mbps, 12 mbps, and 24 mbps respectively, so datatransmission at 48 mbps is realized on the entire system.

As already described above, according to the present invention, ascrambling/descrambling initial value can be extracted for each physicallayer header section based on a rule common with an other party ofcommunication.

When transmitting the transmission frame, using the scrambling initialvalue extracted from the physical layer header section (PHY header) 1the subsequent physical layer header section (PHY header) 2 isscrambled.

As shown in FIG. 31, physical layer header sections (PHY headers) 2through 5 are provided for each MIMO channel, and these are transmittedin order using time division multiplexing. At this time, the physicallayer header section (PHY header) 3 is scrambled using the scramblinginitial value extracted from the physical layer header section (PHYheader) 2, and hereinafter in the same way, the physical layer headersection (PHY header) 4 is scrambled using the scrambling initial valueextracted from the physical layer header section (PHY header) 3, and thephysical layer header section (PHY header) 5 is scrambled using thescrambling initial value extracted from the physical layer headersection (PHY header) 4.

Subsequently, the data section over each channel subjected tospace-division multiplexing is scrambled using the scrambling initialvalue to be extracted from the corresponding physical layer headersection. That is to say, using the scrambling initial value extractedfrom the physical layer header section (PHY header) 2 the data section(DATA) 2 over the corresponding channel is scrambled, using thescrambling initial value extracted from the physical layer headersection (PHY header) 3 the data section (DATA) 3 over the correspondingchannel is scrambled, using the scrambling initial value extracted fromthe physical layer header section (PHY header) 4 the data section (DATA)4 over the corresponding channel is scrambled, and using the scramblinginitial value extracted from the physical layer header section (PHYheader) 5 the data section (DATA) 5 over the corresponding channel isscrambled.

On the other hand, at the time of reception, the descrambling initialvalue is extracted from the physical layer header section (PHY header) 1not scrambled.

Subsequently, the physical layer header sections (PHY headers) 2 through5 for each MIMO channel are received in order using time divisionmultiplexing, but at this time, the physical layer header section (PHYheader) 2 is descrambled using the descrambling initial value extractedfrom the physical layer header section (PHY header) 1, and hereinafterin the same way, the physical layer header section (PHY header) 3 isdescrambled using the descrambling initial value extracted from thephysical layer header section (PHY header) 2, the physical layer headersection (PHY header) 4 is descrambled using the descrambling initialvalue extracted from the physical layer header section (PHY header) 3,and the physical layer header section (PHY header) 5 is descrambledusing the descrambling initial value extracted from the physical layerheader section (PHY header) 4.

Subsequently, upon the data section subjected to space-divisionmultiplexing being received over each channel, the received data sectionis subjected to scrambling using the descrambling initial value to beextracted from the corresponding physical layer header section. That isto say, using the descrambling initial value extracted from the physicallayer header section (PHY header) 2 the data section (DATA) 2 over thecorresponding channel is descrambled, using the descrambling initialvalue extracted from the physical layer header section (PHY header) 3the data section (DATA) 3 over the corresponding channel is descrambled,using the descrambling initial value extracted from the physical layerheader section (PHY header) 4 the data section (DATA) 4 over thecorresponding channel is descrambled, and using the descrambling initialvalue extracted from the physical layer header section (PHY header) 5the data section (DATA) 5 over the corresponding channel is descrambled.

Note that with the present embodiment of the present invention,description has been made regarding the example wherein a packet to bescrambled and the scrambling initial value thereof are generated withinthe same packet, but not restricted to the packet to be scrambled, andthe value within another packet may be used as well. For example, in theevent that data length is always the same, meaning that signal fieldsare fixed, such as AV transmission, it can be conceived that with thetransmission device side, the last 7-bit data (e.g., the 4th byte ofCRC) of the packet of which the reception acknowledgement signal (ACK)could be received immediately before transmission is employed as aninitial value when scrambling the next packet to be transmitted. In thiscase, on the reception device side, the last 7-bit data of the packet ofwhich the reception acknowledgement signal was returned immediatelybefore reception is employed as an initial value when descrambling thenext packet to be received.

However, in this case, there is the possibility that the transmissionside failed to receive the reception acknowledgement signal, andtransmits the last packet using the last initial value, so that it iseffective to prepare and select two types of initial values using twodescramblers such as shown in the above FIG. 20. Also, in this case, ifmultiple terminals exist as to one access point, multiple packets whichanswered back the reception acknowledgement signal exist as well,resulting in vexatious complication, and accordingly, this arrangementis particularly effective for being applied to a system wherein oneterminal exists as to one access point.

Note that the embodiment of the present invention shows an example forrealizing the present invention, and has a corresponding relation as toeach of the invention identification items in the Claims such as shownin the following, but is not restricted to this, and can be applied tovarious modifications without departing from the essence of the presentinvention.

For example, with claims 4 and 5, the signal converting means correspondto the scrambler 220, and the internal state thereof corresponds to thevalues held by the shift registers 224 and 225, for example. Also, theinitial-value setting means correspond to the shift register 222 and theselector 223, for example.

Also, with claim 7, the header generating means correspond to the headergenerating unit 210.

Also, with claims 8 and 14, the parity signal included in the physicallayer header corresponds to the parity bit 624, for example.

Also, with claim 9, the signal converting means correspond to thescrambler 220 for example, and the internal state thereof corresponds tothe values held by the shift registers 224 and 225 for example. Also,the initial-value setting instructing means correspond to theinitial-value setting flag 211, for example. Also, the initial-valuesetting means correspond to the shift register 222 and the selector 223,for example. Also, the header generating means correspond to the headergenerating unit 210.

Also, with claim 10, the initial-value register corresponds to the shiftregister 222, for example. Also, the first shift register corresponds tothe shift register 224, for example. Also, the second shift registercorresponds to the shift register 225, for example. Also, the firstcalculator corresponds to the exclusive-OR circuit 226, for example.Also, the selector corresponds to the selector 223, for example. Also,the second calculator corresponds to the exclusive-OR circuit 227, forexample. Also, the control means correspond to the control unit 221, forexample.

Also, with claim 11, the signal converting means correspond to thedescrambler 270 for example, and the internal state thereof correspondsto the values held by the shift registers 274 and 275 for example. Also,the initial-value setting means correspond to the shift register 272 andthe selector 273, for example. Also, the signal indicating initializingtiming corresponds to the scrambler initialization 651, for example.

Also, with claim 12, the signal converting means correspond to thedescrambler 270 for example, and the internal state thereof correspondsto the values held by the shift registers 274 and 275 for example. Also,the header analyzing means correspond to the header analyzing unit 280,for example. Also, the initial-value setting means correspond to theshift register 272 and the selector 273, for example.

Also, with claim 15, the initial-value register corresponds to the shiftregister 272, for example. Also, the first shift register corresponds tothe shift register 274, for example. Also, the second shift registercorresponds to the shift register 275, for example. Also, the firstcalculator corresponds to the exclusive-OR circuit 276, for example.Also, the selector corresponds to the selector 273, for example. Also,the second calculator corresponds to the exclusive-OR circuit 277, forexample. Also, the control means correspond to the control unit 271, forexample.

Also, with claim 16, the descramblers correspond to the descrambler 270or 290, for example. Also, the selector corresponds to the selector 303,for example. Also, the error determining means correspond to the errordetermining unit 305, for example.

Also, with claim 3, the first signal converting means correspond to thescrambler 220 for example, and the internal state thereof corresponds tothe values held by the shift registers 224 and 225 for example. Also,the initial-value setting instructing means correspond to theinitial-value setting flag 211, for example. Also, the firstinitial-value setting means correspond to the shift register 222 and theselector 223, for example. Also, the header generating means correspondto the header generating unit 210, for example. The second signalconverting means correspond to the descrambler 270 for example, and theinternal state thereof corresponds to the values held by the shiftregisters 274 and 275 for example. Also, the header analyzing meanscorrespond to the header analyzing unit 280, for example. Also, thesecond initial-value setting means correspond to the shift register 272and the selector 273, for example.

Also, with claims 43 and 46, the procedure for generating a physicallayer header of a transmission packet corresponds to Step S911, forexample. Also, in the event of the initial-value setting instructingmeans indicating that an initial value should be set in the internalstate, the procedure for inverting a parity signal in the physical layerheader, and setting predetermined data included in the physical layerheader as the initial value of the internal state of the scramblercorresponds to Steps S912, S915, and S916, for example. Also, theprocedure for subjecting a signal to be processed in a transmissionpacket to predetermined arithmetic operation depending on the internalstate of the scrambler, and outputting this, corresponds to Step S917,for example.

Also, with claims 44 and 47, the procedure for analyzing the physicallayer header of a reception packet corresponds to Step S921. Also, theprocedure for setting the headmost data of a signal to be processed asthe initial value of the internal state of the descrambler in the eventof a normal value being set in the parity signal of the physical layerheader, and setting predetermined data included in the physical layerheader other than the signal to be processed as the initial value of theinternal state of the descrambler in the event of an abnormal valuebeing set in the parity signal of the physical layer header as theinitial value setting information, corresponds to Steps S922, S924, andS926, for example. Also, the procedure for subjecting a signal to beprocessed to predetermined arithmetic operation depending on theinternal state of the descrambler, and outputting this, corresponds toStep S927, for example.

Note that the procedures described in the embodiment of the presentinvention may be regarded as a method including these series ofprocedures, or may be regarded as a program for causing a computer toexecute these series of procedures or a recording medium storing theprogram.

INDUSTRIAL APPLICABILITY

As described above, description has been made in detail regarding thepresent invention with reference to the particular embodiment. However,it is fully apparent that one skilled in the art can make variousmodifications and substitutions to the embodiment without departing fromthe essence of the present invention.

With the present specification, the embodiment of the present inventionhas been described based on IEEE802.11serving as the standardspecifications of a wireless LAN system, but the essence of the presentinvention is not restricted to this, and the present invention can beapplied in the same way to other communication systems which requirescrambling/descrambling between transmission and reception, and alsonotifying and sharing a scrambling initial value between transmissionand reception.

In other words, the present invention has been disclosed in an exemplaryform, and the contents of the description in the present specificationshould not be interpreted in a restrictive manner. In order to determinethe essence of the present invention, the Claims should be referenced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating the entire configurationof a communication system according to an embodiment of the presentinvention.

FIG. 2 is a diagram schematically illustrating the functionalconfiguration of a transmitter according to an embodiment of the presentinvention.

FIG. 3 is a diagram schematically illustrating the functionalconfiguration of a receiver according to an embodiment of the presentinvention.

FIG. 4 is a diagram illustrating the configuration of a scrambler 516disposed in a wireless communication apparatus 500.

FIG. 5 is a diagram illustrating the configuration of around adescrambler 658 disposed in a wireless communication apparatus 600.

FIG. 6 is a diagram illustrating the internal configuration of ascrambler according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating the internal configuration of adescrambler according to an embodiment of the present invention.

FIG. 8 is a flowchart illustrating the scrambling procedures in atransmission device according to an embodiment of the present invention.

FIG. 9 is a flowchart illustrating the descrambling procedures in areception device according to an embodiment of the present invention.

FIG. 10 is a diagram for describing a first modification example of anembodiment of the present invention.

FIG. 11 is a diagram illustrating the configuration of a conventionaldescrambler 290.

FIG. 12 is a diagram illustrating the configuration of an MAC frame inthe IEEE802.11standard.

FIG. 13 is a diagram for describing a second modification example of anembodiment of the present invention.

FIG. 14 is a diagram illustrating the configurations of physical headerinformation and a data field to be used for a wireless network accordingto the present invention.

FIG. 15 is a diagram for describing a first method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 16 is a diagram for describing a second method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 17 is a diagram for describing a third method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 18 is a diagram for describing a fourth method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 19 is a diagram for describing a fifth method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 20 is a diagram for describing a sixth method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 21 is a diagram for describing a seventh method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 22 is a diagram for describing an eighth method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 23 is a diagram for describing a ninth method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 24 is a diagram for describing a tenth method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 25 is a diagram for describing an eleventh method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 26 is a diagram for describing a twelfth method for generating ascrambling initial value and a descrambling initial value based onphysical layer header information.

FIG. 27 is a diagram illustrating a configuration example of onetransmission frame including multiple fields not scrambled.

FIG. 28 is a diagram illustrating a configuration example of onetransmission frame including multiple fields not scrambled.

FIG. 29 is a diagram illustrating a configuration example of onetransmission frame including two or more physical layer header sections,following which a data section continuing.

FIG. 30 is a diagram illustrating a configuration example of onetransmission frame in which multiple pairs made up of a physical layerheader section and a data section continue.

FIG. 31 is a diagram illustrating a configuration example of atransmission frame format available for an MIMO communication method.

FIG. 32 is a diagram illustrating a configuration example of a wirelesscommunication apparatus employed for the IEEE802.11a.

FIG. 33 is a diagram illustrating the configuration of a scrambler 116disposed in the transmission system of a wireless communicationapparatus 100.

FIG. 34 is a diagram illustrating the configuration of a descrambler 158disposed in the reception system of the wireless communication apparatus100.

FIG. 35 is a diagram illustrating an OFDM signal format stipulated bythe IEEE802.11a.

FIG. 36 is a diagram illustrating the configuration of a PHY header indetail.

FIG. 37 is a diagram illustrating the configuration of around thescrambler 116 on the transmission side.

FIG. 38 is a diagram illustrating the configuration of around thedescrambler 158 on the reception side.

1. A wireless communication system for communicating transmission datacomprising: a physical layer header section; and a data section; whereinon the transmission side, a scrambling initial value is generated usingat least a part of a physical header section, and scrambling of a datasection is performed using the scrambling initial value; and wherein onthe reception side, a descrambling initial value is generated using atleast a part of a physical header, and descrambling of a data section isperformed using the descrambling initial value.
 2. A wirelesscommunication system for communicating transmission data comprising: anon-scrambled section; and a scrambled section; wherein on thetransmission side, a scrambling initial value is generated using atleast a part of a non-scrambled section, and in the event that thegenerated scrambling initial value is made up of all zero bits, theseare replaced with a known bit sequence other than all zero bits, andscrambling of a scrambled section is performed using the scramblinginitial value; and wherein on the reception side, a descrambling initialvalue is generated using at least a part of a non-scrambled section, andin the event that the generated descrambling initial value is made up ofall zero bits, these are replaced with a known bit sequence other thanall zero bits, and descrambling of a scrambled section is performedusing the descrambling initial value.
 3. A communication systemcomprising: a transmission device for transmitting transmission packets;and a reception device for receiving said transmission packets asreception packets; said transmission device having first signalconverting means for subjecting a signal to be processed in saidtransmission packet to a predetermined arithmetic operation according toan internal state, and outputting the signal, initial-value settinginstructing means for indicating regarding whether or not an initialvalue should be set in the internal state of said first signalconverting means, first initial-value setting means for settingpredetermined data included in a physical layer header of saidtransmission packet as an initial value in the internal state of saidfirst signal converting means in the event that this initial-valuesetting instructing means indicate that an initial value should be setin said internal state, and header generating means for setting initialvalue setting information indicating regarding whether or not this firstinitial-value setting means performed said initial value setting to saidphysical layer header; and said reception device having second signalconverting means for subjecting a signal to be processed in saidreception packet to a predetermined arithmetic operation according to aninternal state, and outputting the signal, header analyzing means foranalyzing a physical layer header of said reception packet, andextracting said initial value setting information, and secondinitial-value setting means for setting predetermined data included insaid physical layer header other than said signal to be processed as aninitial value in the internal state of said second signal convertingmeans in the event that said initial value setting information indicatesthat said initial value setting was performed, and setting the headmostdata of said signal to be processed as an initial value in the internalstate of said second signal converting means in the event that saidinitial value setting information indicates that said initial valuesetting was not performed.
 4. A transmission device comprising: signalconverting means for subjecting a signal to be processed in atransmission packet to a predetermined arithmetic operation according toan internal state, and outputting the signal; and initial-value settingmeans for setting predetermined data included in said transmissionpacket as an initial value in the internal state of said signalconverting means.
 5. The transmission device according to claim 4,wherein said initial-value setting means set predetermined data includedin a physical layer header of said transmission packet as an initialvalue in the internal state of said signal converting means.
 6. Thetransmission device according to claim 5, wherein said predetermineddata is the lower 7 bits of a data length field.
 7. The transmissiondevice according to claim 5 further comprising: header generating meansfor generating said physical layer header; wherein said headergenerating means set initial value setting information indicating thatthe initial value in the internal state of said signal converting meansis set, in said physical layer header.
 8. The transmission deviceaccording to claim 7, wherein said header generating means set anabnormal value in a parity signal included in said physical layer headeras said initial value setting information.
 9. The transmission deviceaccording to claim 4 further comprising: initial-value settinginstructing means for indicating regarding whether or not an initialvalue should be set in the internal state of said signal convertingmeans; and header generating means for generating said physical layerheader; wherein said initial-value setting means set predetermined dataincluded in a physical layer header of said transmission packet as aninitial value in the internal state of said signal converting means inthe event that said initial-value setting instructing means indicatethat an initial value should be set in said internal state; and whereinsaid header generating means set initial value setting informationindicating regarding whether or not said initial-value setting meansperformed said initial value setting, in said physical layer header. 10.A transmission device comprising: an initial-value register for holdingpredetermined data included in a transmission packet; a first shiftregister; a second shift register of which an input portion is connectedto an output portion of said first shift register; a first calculatorfor inputting the output data of said first shift register and theoutput data of said second shift register, and subjecting the input datato an exclusive-OR operation; a selector for outputting either theoutput of said initial-value register or the output of said firstcalculator to the input portion of said first shift register; a secondcalculator for inputting the output data of said selector and the signalto be processed in said transmission packet, and subjecting the inputdata to an exclusive-OR operation; and control means for controllingsaid selector such that the output of said initial-value register isoutput to the input portion of said first register when an initial valuesignal is input to said second calculator as said signal to beprocessed, following which the output of said first calculator is outputto the input portion of said first shift register.
 11. A receptiondevice comprising: signal converting means for subjecting a signal to beprocessed in a reception packet to a predetermined arithmetic operationaccording to an internal state, and outputting the signal; andinitial-value setting means for setting predetermined data other than asignal indicating the initializing timing of said signal convertingmeans in said reception packet as an initial value in the internal stateof said signal converting means.
 12. The reception device according toclaim 11, further comprising: header analyzing means for analyzing aphysical layer header of said reception packet, and extracting initialvalue setting information; wherein said initial-value setting means seteither the headmost data of said signal to be processed or predetermineddata included in said physical layer header other than said signal to beprocessed as an initial value in the internal state of said signalconverting means according to said initial value setting information.13. The reception device according to claim 12, wherein saidpredetermined data is the lower 7 bits of a data length field.
 14. Thereception device according to claim 12, wherein said initial-valuesetting means set the headmost data of said signal to be processed as aninitial value in the internal state of said signal converting means, inthe event that a normal value is set in a parity signal of said physicallayer header as said initial value setting information, and setpredetermined data included in said physical layer header other thansaid signal to be processed as an initial value in the internal state ofsaid signal converting means, in the event that an abnormal value is setin the parity signal of said physical layer header as said initial valuesetting information.
 15. A reception device comprising: an initial-valueregister for holding predetermined data included in a reception packet;a first shift register; a second shift register of which an inputportion is connected to an output portion of said first shift register;a first calculator for inputting the output data of said first shiftregister and the output data of said second shift register, andsubjecting the input data to an exclusive-OR operation; a selector foroutputting either the output of said initial-value register or theoutput of said first calculator to the input portion of said first shiftregister; a second calculator for inputting the output data of saidselector and the signal to be processed in said reception packet, andsubjecting the input data to an exclusive-OR operation; and controlmeans for controlling said selector such that the output of saidinitial-value register is output to the input portion of said firstregister when an initial value signal is input to said second calculatoras said signal to be processed, following which the output of said firstcalculator is output to the input portion of said first shift register.16. A reception device comprising: multiple descramblers for subjectinga signal to be scrambled in a reception packet to descrambling accordingto each internal state, and outputting the signal; a selector foroutputting any output of said multiple descramblers; and errordetermining means for controlling said selector so as to analyze theoutputs from said multiple descramblers and select the output satisfyingranges stipulated in all fields, of these outputs.
 17. A wirelesscommunication apparatus for communicating transmission data made up of aphysical layer header section and a data section, said apparatuscomprising: communication means for transmitting/receiving transmissiondata over a communication channel; scrambling/descrambling initial-valuegenerating means for generating an initial value when scrambling ordescrambling using at least a part of a physical layer header section;and scrambling/descrambling means for performing scrambling ordescrambling of a data section using said initial value.
 18. Thewireless communication apparatus according to claim 17, wherein saidscrambling/descrambling means generate a transmission signal sequencescrambled by calculating an exclusive-OR operation between a scrambledsequence generated from a scrambling initial value and a transmissiondata sequence, or descramble a reception data sequence by calculating anexclusive-OR operation between a descrambled sequence generated from adescrambling initial value and a reception signal sequence scrambled.19. The wireless communication apparatus according to claim 17, whereinin the event that said initial value when scrambling/descrambling is nbits in length (wherein n is a natural number), saidscrambling/descrambling initial-value generating means take an n-bitsequence obtained by extracting n bits from a physical layer headersection or a part thereof based on a rule common with an other party ofcommunication, as said initial value when scrambling/descrambling. 20.The wireless communication apparatus according to claim 19, wherein saidscrambling/descrambling initial-value generating means generate saidinitial value when scrambling/descrambling by extracting n bitsincluding fields of which all bits are not zero, of a physical layerheader section.
 21. The wireless communication apparatus according toclaim 19, wherein said scrambling/descrambling initial-value generatingmeans take a fixed n-bit sequence, which are not all zero bits, sharedwith an other party of communication as said initial value whenscrambling/descrambling, in the event that n bits extracted from aphysical layer header section are all zeroes.
 22. The wirelesscommunication apparatus according to claim 17, wherein in the event thatsaid initial value when scrambling/descrambling is n bits in length(wherein n is a natural number), said scrambling/descramblinginitial-value generating means extract (n−k) bits from a physical layerheader section or a part thereof based on a rule common with an otherparty of communication (wherein k is a natural number smaller than n),and insert a k-bit sequence such that at least 1 bit thereof includeslogic “1”, shared with the other party of communication in the extractedbit sequence of said (n−k) bits in a pattern shared with the other partyof communication, and generate said initial value whenscrambling/descrambling.
 23. The wireless communication apparatusaccording to claim 17, wherein in the event that said initial value whenscrambling/descrambling is n bits in length (wherein n is a naturalnumber), said scrambling/descrambling initial-value generating meanscount the number of logics “1” in said physical layer header section ora part thereof, represent the number thereof with n bits in binary, andtake this as said initial value when scrambling/descrambling.
 24. Thewireless communication apparatus according to claim 23, wherein in theevent that the number of logics “1” counted in said physical layerheader section or a part thereof is zero, said scrambling/descramblinginitial-value generating means take a fixed n-bit sequence, which arenot all zero bits, shared with an other party of communication as saidinitial value when scrambling/descrambling.
 25. The wirelesscommunication apparatus according to claim 17, wherein in the event thatsaid initial value when scrambling/descrambling is n bits in length(wherein n is a natural number), said scrambling/descramblinginitial-value generating means count the number of logics “1” in saidphysical layer header section or a part thereof, represent the numberthereof with (n−m) bits in binary (wherein m is a natural number smallerthan n), and insert an m-bit sequence such that at least 1 bit thereofincludes logic “1”, shared with an other party of communication in theextracted bit sequence of said (n−m) bits in a pattern shared with theother party of communication, and generate said initial value whenscrambling/descrambling.
 26. The wireless communication apparatusaccording to claim 17, wherein in the event that said initial value whenscrambling/descrambling is n bits in length (wherein n is a naturalnumber), said scrambling/descrambling initial-value generating meanscount the number of logics “1” in said physical layer header section ora part thereof, add x shared with an other party of communication(wherein x is a natural number smaller than 2n) to the number thereof,represent the result with n bits in binary, and take this bit sequenceas said initial value when scrambling/descrambling.
 27. The wirelesscommunication apparatus according to claim 17, wherein in the event thatsaid initial value when scrambling/descrambling is n bits in length(wherein n is a natural number), said scrambling/descramblinginitial-value generating means count the number of logics “0” in saidphysical layer header section or a part thereof, represent the numberthereof with n bits in binary, and take this as said initial value whenscrambling/descrambling.
 28. The wireless communication apparatusaccording to claim 17, wherein in the event that the number of logics“0” counted in said physical layer header section or a part thereof iszero, said scrambling/descrambling initial-value generating means take afixed n-bit sequence, which are not all zero bits, shared with an otherparty of communication as said initial value whenscrambling/descrambling.
 29. The wireless communication apparatusaccording to claim 17, wherein in the event that said initial value whenscrambling/descrambling is n bits in length (wherein n is a naturalnumber), said scrambling/descrambling initial-value generating meanscount the number of logics “0” in said physical layer header section ora part thereof, represent the number thereof with (n−m) bits in binary(wherein h is a natural number smaller than n), insert an h-bit sequencesuch that at least one bit thereof is logic “1”, shared with an otherparty of communication in the extracted bit sequence of said (n−h) bitsin a pattern shared with the other party of communication, and generatesaid initial value when scrambling/descrambling.
 30. The wirelesscommunication apparatus according to claim 17, wherein in the event thatsaid initial value when scrambling/descrambling is n bits in length(wherein n is a natural number), said scrambling/descramblinginitial-value generating means count the number of logics “0” in saidphysical layer header section or a part thereof, add y shared with another party of communication (wherein y is a natural number smaller than2n) to the number thereof, represent the result with n bits in binary,and take this bit sequence as said initial value whenscrambling/descrambling.
 31. The wireless communication apparatusaccording to claim 17, wherein in the event that said initial value whenscrambling/descrambling is n bits in length (wherein n is a naturalnumber), said scrambling/descrambling initial-value generating meanscount the number of logics “1” and the number of logics “0” in saidphysical layer header section or a part thereof respectively, andrepresent the absolute value of the difference thereof with n bits inbinary, and take this as said initial value whenscrambling/descrambling.
 32. The wireless communication apparatusaccording to claim 31, wherein in the event that the difference betweenthe number of logics “1” and the number of logics “0” in said physicallayer header section or a part thereof is zero, saidscrambling/descrambling initial-value generating means take a fixedn-bit sequence, which are not all zero bits, shared with an other partyof communication as said initial value when scrambling/descrambling. 33.The wireless communication apparatus according to claim 17, wherein inthe event that said initial value when scrambling/descrambling is n bitsin length (wherein n is a natural number), said scrambling/descramblinginitial-value generating means count the number of logics “1” and thenumber of logics “0” in said physical layer header section or a partthereof respectively, represent the absolute value of the differencethereof with (n−i) bits in binary, insert an i-bit sequence such that atleast one bit thereof is logic “1”, shared with an other party ofcommunication in the extracted bit sequence of said (n−i) bits in apattern shared with the other party of communication, and generate saidinitial value when scrambling/descrambling.
 34. The wirelesscommunication apparatus according to claim 17, wherein in the event thatsaid initial value when scrambling/descrambling is n bits in length(wherein n is a natural number), said scrambling/descramblinginitial-value generating means count the number of logics “1” and thenumber of logics “0” in said physical layer header section or a partthereof respectively, obtain the absolute value of the differencethereof, add z shared with an other party of communication (wherein z isa natural number smaller than 2n) to the absolute value, represent theresult with z bits in binary, and take this bit sequence as said initialvalue when scrambling/descrambling.
 35. A wireless communicationapparatus for communicating transmission data made up of a non-scrambledsection and a scrambled section, said apparatus comprising:communication means for transmitting/receiving transmission data over acommunication channel; scrambling/descrambling initial-value generatingmeans for generating an initial value when scrambling/descrambling usingat least a part of a non-scrambled section, and replacing the initialvalue with a known bit sequence, which are not all zero bits, in theevent that the generated initial value is made up of all zero bits; andscrambling/descrambling means for performing scrambling or descramblingof a scrambled section using said initial value.
 36. A wirelesscommunication apparatus for communicating transmission data made up ofone or more pairs of a physical layer header section and a data section,said apparatus comprising: scrambling/descrambling initial-valueacquiring means for acquiring an initial value when scrambling ordescrambling from each physical layer header section; andscrambling/descrambling means, using an initial value extracted from aphysical layer header section, for performing scrambling or descramblingof the data section to be coupled with the physical layer headersection.
 37. The wireless communication apparatus according to claim 36,wherein in the event of including a non-scrambled signal between aphysical layer header section and a data section, saidscrambling/descrambling means delays the start position of scrambling ordescrambling of a data section by a predetermined period correspondingto transmission and reception of a non-scrambled section followingtransmission or reception of a physical layer header section.
 38. Awireless communication apparatus for communicating transmission dataincluding two or more physical layer header sections, said apparatuscomprising: scrambling/descrambling initial-value acquiring means foracquiring an initial value when scrambling or descrambling from eachphysical layer header section; and scrambling/descrambling means forperforming scrambling or descrambling of the subsequent signals usingthe initial value extracted from each physical layer header section. 39.The wireless communication apparatus according to claim 38, whereinfollowing the next physical layer header section appearing until saidscrambling/descrambling initial-value acquiring means acquire an initialvalue when scrambling or descrambling, said scrambling/descramblingmeans perform scrambling or descrambling of the subsequent signalscontinuously using the initial value when scrambling or descrambling,which has been acquired last.
 40. A wireless communication apparatus forperforming space-division multiplexing communication, wherein eachphysical layer header section corresponding to a data section over eachchannel subjected to space-division multiplexing is transmitted by timedivision.
 41. The wireless communication apparatus according to claim40, further comprising: scrambling/descrambling initial-value acquiringmeans for acquiring an initial value when scrambling or descramblingfrom each physical layer header section; and scrambling/descramblingmeans, using the initial value extracted from each physical layer headersection, for performing scrambling or descrambling of the data sectionto be transmitted over the corresponding channel.
 42. The wirelesscommunication apparatus according to claim 36, wherein saidscrambling/descrambling initial-value acquiring means generate aninitial value when scrambling or descrambling using at least a part of aphysical layer header section based on a rule common with an other partyof communication.
 43. A processing method for processing transmissionpackets based on an initial-value setting instructing step indicatingregarding whether or not an initial value should be set in an internalstate possessed by a scrambler, said method comprising: a procedure forgenerating a physical layer header of a transmission packet; a procedurefor inverting a parity signal in said physical layer header, and settingpredetermined data included in said physical layer header as an initialvalue in the internal state of said scrambler, in the event ofindicating that an initial value should be set in said internal state;and a procedure for subjecting a signal to be processed in saidtransmission packet to a predetermined arithmetic operation according tothe internal state of said scrambler, and outputting this.
 44. Aprocessing method for processing reception packets by subjecting asignal to be processed in each reception packet to a predeterminedarithmetic operation according to an internal state possessed by adescrambler, said method comprising: a procedure for analyzing aphysical layer header of a reception packet; a procedure for setting theheadmost data of said signal to be processed as an initial value in theinternal state of said descrambler in the event that a normal value isset in a parity signal of said physical layer header as initial valuesetting information, and setting predetermined data included in saidphysical layer header other than said signal to be processed as aninitial value in the internal state of said descrambler in the eventthat an abnormal value is set in a parity signal of said physical layerheader as said initial value setting information; and a procedure forsubjecting said signal to be processed to said predetermined arithmeticoperation according to the internal state of said descrambler, andoutputting this.
 45. A wireless communication method for controllingcommunication operation of transmission data made up of a physical layerheader section and a data section, said method comprising: ascrambling/descrambling initial-value generating step for generating aninitial value when scrambling or descrambling using at least a part of aphysical layer header section based on a rule common with an other partyof communication; and a scrambling/descrambling step for performingscrambling or descrambling of a data section using said initial value.46. A computer program which is described in a computer-readable formatso as to execute the processing of transmission packets on a computersystem based on initial value setting instructions indicating regardingwhether or not an initial value should be set in an internal statepossessed by a scrambler, said program comprising: a procedure forgenerating a physical layer header of a transmission packet; a procedurefor inverting a parity signal in said physical layer header, and settingpredetermined data included in said physical layer header as an initialvalue in the internal state of said scrambler, in the event ofindicating that an initial value should be set in said internal state;and a procedure for subjecting a signal to be processed in saidtransmission packet to a predetermined arithmetic operation according tothe internal state of said scrambler, and outputting this.
 47. Acomputer program which is described in a computer-readable format so asto execute the processing of reception packets on a computer systemwherein a signal to be processed in each reception packet is subjectedto a predetermined arithmetic operation according to an internal statepossessed by a descrambler, said program comprising: a procedure foranalyzing a physical layer header of a reception packet; a procedure forsetting the headmost data of said signal to be processed as an initialvalue in the internal state of said descrambler in the event that anormal value is set in a parity signal of said physical layer header asinitial value setting information, and setting predetermined dataincluded in said physical layer header other than said signal to beprocessed as an initial value in the internal state of said descramblerin the event that an abnormal value is set in a parity signal of saidphysical layer header as said initial value setting information; and aprocedure for subjecting said signal to be processed to saidpredetermined arithmetic operation according to the internal state ofsaid descrambler, and outputting this.
 48. A computer program which isdescribed in a computer-readable format so as to execute control ofcommunication operation of transmission data made up of a physical layerheader section and a data section on a computer system, said programcomprising: a scrambling/descrambling initial-value generating step forgenerating an initial value when scrambling or descrambling using atleast a part of a physical layer header section based on a rule commonwith an other party of communication; and a scrambling/descrambling stepfor performing scrambling or descrambling of a data section using saidinitial value.
 49. The wireless communication apparatus according toclaim 38, wherein said scrambling/descrambling initial-value acquiringmeans generate an initial value when scrambling or descrambling using atleast a part of a physical layer header section based on a rule commonwith an other party of communication.
 50. The wireless communicationapparatus according to claim 41, wherein said scrambling/descramblinginitial-value acquiring means generate an initial value when scramblingor descrambling using at least a part of a physical layer header sectionbased on a rule common with an other party of communication.